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-The Unix Hardware Buyer HOWTO
-!!!The Unix Hardware Buyer HOWTO
-!Eric Raymond
-
- esr@thyrsus.com
-
-
-
-__Revision History__Revision 2.02001-08-09Revised by: esrMajor update. Revisions based on Ultimate Linux Box experience.
-Caches are on-chip now. DDS4 tape drives are here.
-486 machines, CD caddies, and most non-DDS backup
-technologies are goneRevision 1.12001-06-13Revised by: esrMid-2001 update.Revision 1.02001-02-06Revised by: esrInitial revision; but see the history in the introduction.
-
-
-
-
-
-This is your one-stop resource for information about how to buy and
-configure Intel hardware for cheap, powerful Unix systems.
-
-
-
-
-
-
-----; __Table of Contents__; 1. Introduction: ; 1.1. Purpose and History; 1.2. New versions of this document; 1.3. Feedback and corrections; 1.4. Related resources; 2. Overview of the Market; 3. Buying the Basics: ; 3.1. Getting Down to Cases; 3.2. Power Supplies and Fans; 3.3. Motherboards; 3.4. Memory; 3.5. Buying a Video Card; 3.6. Selecting a Monitor: ; 3.6.1. What To Look For On The Spec Sheet.; 3.6.2. Eric Buys A Big Monitor: Smart Shopping Tips; 3.7. Keyboards; 3.8. Floppy Drives; 3.9. Printers: ; 3.9.1. GDI printers: avoid!; 3.9.2. Non-GDI printers; 3.10. Power Protection: ; 3.10.1. Overview; 3.10.2. Surge suppressors; 3.10.3. Line Conditioners; 3.10.4. Standby power supplies (SPSs); 3.10.5. Uninterruptable power supplies (UPSs); 3.11. Radio Frequency Interference; 4. Performance Tuning: ; 4.1. How To Pick Your Processor; 4.2. Of Memory In...; 4.3. Bus Wars: ; 4.3.1. Bus Types; 4.4. Disk Wars: IDE vs. SCSI: ; 4.4.1. Overview; 4.4.2. Enhanced IDE; 4.4.3. SCSI Terminology: ; 4.4.3.1. Logical: SCSI-1, SCSI-2, SCSI-3; 4.4.3.2. Electrical Interface; 4.4.3.3. Handshake; 4.4.3.4. Synchronous Speed (does not apply for asynchronous option); 4.4.3.5. Path width; 4.4.4. Avoiding Pitfalls; 4.4.5. Trends to Watch For; 4.4.6. More Resources; 4.5. Other Disk Decisions: ; 4.5.1. Disk Brands; 4.6. Tuning Your I/O Subsystem; 4.7. Souping Up X Performance; 5. Hardware for Backups; 6. Of Mice And Machines: ; 6.1. Mouse Types; 6.2. Buying a Mouse; 7. Modems: ; 7.1. The Simple Answer; 7.2. Overview of the Modem Market; 7.3. Internal vs. External; 7.4. Pitfalls to Avoid; 7.5. What to Buy; 7.6. Fax Modems; 8. CD-ROMs and Multimedia Hardware: ; 8.1. CD-ROM Drives; 8.2. Sound Cards and Speakers; 9. Special considerations when buying laptops; 10. How to Buy: ; 10.1. When to Buy; 10.2. Where to Buy; 10.3. Computer Fairs; 10.4. Mail Order; 10.5. Computer Superstores; 10.6. Other Buying Tips; 11. Questions You Should Always Ask Your Vendor: ; 11.1. Minimum Warranty Provisions; 11.2. Documentation; 11.3. A System Quality Checklist; 12. Things to Check when Buying Mail-Order: ; 12.1. Tricks and Traps in Mail-Order Warranties; 12.2. Special Questions to Ask Mail-Order Vendors Before Buying; 12.3. Payment Method; 12.4. Which Clone Vendors to Talk To: ; 12.4.1. Some pans; 12.4.2. Some picks; 13. After You Take Delivery; 14. Software to go with your hardware; 15. Other Resources on Building Linux PCs; 16. Upgrading Older Machines: ; 16.1. Older Memory Types----
-!!!1. Introduction
-!!1.1. Purpose and History
-
-The purpose of this document is to give you the background
-information you need to be a savvy buyer of Intel hardware for running
-Unix. It is aimed especially at hackers and others with the technical
-skills and confidence to go to the mail-order channel, but contains
-plenty of useful advice for people buying store-front retail.
-
-
-
-This document is maintained and periodically updated as a
-service to the net by Eric S. Raymond, who began it for the very best
-self-interested reason that he was in the market and didn't believe in
-plonking down several grand without doing his homework first (no, I
-don't get paid for this, though I have had a bunch of free software
-and hardware dumped on me as a result of it!). Corrections, updates,
-and all pertinent information are welcomed at esr@snark.thyrsus.com. The
-editorial `we' reflects the generous contributions of many savvy
-Internetters.
-
-
-
-If you email me questions that address gaps in the FAQ material,
-you will probably get a reply that says ``Sorry, everything I know
-about this topic is in the HOWTO''. If you find out the
-''answer'' to such a question, please share it with
-me for the HOWTO, so everyone can benefit.
-
-
-
-If you end up buying something based on information from this
-HOWTO, please do yourself and the net a favor; make a point of telling
-the vendor ``The HOWTO sent me'' or some equivalent. If we can show
-vendors that this HOWTO influences a lot of purchasing decisions, we
-get leverage to change some things that need changing.
-
-
-
-Note that in December 1996 I published an introductory article on
-building and tuning Linux systems summarizing much of the material in
-this HOWTO. It's available
-here.
-
-
-
-This document actually dates back to 1992, when it was known as
-the ``PC-Clone Unix Hardware Buyer's Guide''; this was before Linux
-took over my world :-). Before that, portions of it were part of
-a Unix Buyer's Guide that I maintained back in the 1980s on USENET.
-
-----
-!!1.2. New versions of this document
-
-New versions of the Unix Hardware Buyer HOWTO will be
-periodically posted to comp.os.linux.help and news:comp.os.linux.announce and news.answers. They will also be uploaded to various Linux WWW and
-FTP sites, including the LDP home page.
-
-
-
-You can view the latest version of this on the World Wide Web via the URL
-http://www.linuxdoc.org/HOWTO/Unix-Hardware-Buyer-HOWTO/.
-
-----
-!!1.3. Feedback and corrections
-
-If you have questions or comments about this document, please
-feel free to mail Eric S. Raymond, at esr@thyrsus.com. I welcome any
-suggestions or criticisms. If you find a mistake with this document,
-please let me know so I can correct it in the next
-version. Thanks.
-
-----
-!!1.4. Related resources
-
-You may also want to look at the read the Hardware-HOWTO.
-It lists hardware known to be compatible with Linux, and
-hardware known to be incompatible.
-
-----
-!!!2. Overview of the Market
-
-The central fact about clone hardware that conditions every
-aspect of buying it is this: more than anywhere else in the industry,
-de-facto hardware standards have created a commodity market with low
-entry barriers, lots of competitive pressure, and volume high enough
-to amortize a ''lot'' of development on the
-cheap.
-
-
-
-The result is that this hardware gives you lots of
-bang-per-buck, and it's getting both cheaper and better all the time.
-Furthermore, margins are thin enough that vendors have to be lean,
-hungry, and ''very'' responsive to the market to
-survive. You can take advantage of this, but it does mean that much
-of the info in the rest of this document will be stale in three months
-and completely obsolete in six.
-
-
-
-One good general piece of advice is that you should avoid both
-the highest-end new-technology systems (those not yet shipping in
-volume) and the very cheapest systems put out by vendors competing
-primarily on price. The problem with the high end is that it usually
-carries a hefty ``prestige'' price premium, and may be a bit less
-reliable on average because the technology hasn't been through a lot
-of test/improve cycles. The problem with the low end is that
-price-cutters sometimes settle for marginal components. Unix works
-your hardware more efficiently than DOS or Windows, so it is more
-sensitive to hardware flakiness, which means cut-price systems that
-might deliver consistently for DOS/Windows lemmings can come around
-and bite you. Use a little care, and spend the $200-$300 to stay out
-of the basement. The avoided time and hassles will be worth
-it.
-
-
-
-The last point deserves a little amplification. In the PC world,
-there's a lot of ``if it doesn't fail, it's OK''. It is common to ignore
-normal engineering tolerances (allowances for variations in components,
-temperature, voltage margins, and the like) and to assume that anything
-which doesn't fail outright must work. Watch out! As a historical
-example, the ISA bus was originally designed for 6 MHz. IBM later updated
-that to 8 MHz, and that's as much of a standard as there is, yet there were
-motherboards that will let you (try to!) run it at 12 MHz, 50% over spec.
-Some cards were actually designed to work at that speed with proper
-tolerances. Others might work...or they might flake out when they get
-warm. Any systems vendor above the fly-by-night level is going to shoot
-for a little more reliability than this, burning in systems and (often)
-doing at least a token system test with some kind of Unix (usually Linux
-these days). Pay the few extra bucks it costs to deal with a more careful
-vendor.
-
-
-
-The happy bottom line is this: at July 2001 direct-mail prices, you
-can expect to get an AMD K6 or Pentium III 450 system with 64MB of
-memory, 9gig EIDE hard disk, 3.5 floppy, 101-key keyboard, 32X CD-ROM
-drive, sound card 8 speakers, SuperVGA-compatible 17"
-monitor, 56KB modem, and a decent AGP video card for $800 or even
-less. This is a more than reasonable Unix and X machine.
-
-
-
-I put together the first version of this guide around 1992;
-Unix-capable systems are now five to ten times cheaper than they were
-then. At today's prices, building your own system from parts no
-longer makes much sense at all -- so this HOWTO is now more oriented
-towards helping you configure a whole system from a single vendor.
-
-----
-!!!3. Buying the Basics
-
-In this section, we cover things to look out for that are more or less
-independent of price-performance tradeoffs, part of your minimum system
-for running Unix.
-
-
-
-Issues like your choice of disk, processor, and bus (where there is
-a strong tradeoff between price and capability) are covered in the section
-on performance tuning.
-
-----
-!!3.1. Getting Down to Cases
-
-I used to say that cases are just bent metal, and that it doesn't
-much matter who makes those, as long as they're above an easy minimum
-quality (on some ''really'' cheap ones, cards fail to line
-up nicely with the slots, drive bays don't align with the access cutouts,
-or the motherboard is ill-supported and can ground out against the
-chassis).
-
-
-
-Unfortunately, this isn't true any more. Processors run so hot these
-days that fans and airflow are a serious concern. They need to be well
-designed for proper airflow throughout.
-
-
-
-If you're fussy about RFI (Radio-Frequency Interference), it's worth
-finding out whether the plastic parts of the case have conductive coating
-on the inside; that will cut down emissions significantly, but a few cheap
-cases omit it.
-
-
-
-Look for the following quality features:
-
-
-
-
-
-
-****
-
-Aluminum rather than steel. It's lighter and conducts
-heat better.
-
-
-****
-****
-
-Unobstructed air intake with at least one fan each
-(in addition to the power supply and processor fans)
-
-
-****
-****
-
-No sharp metal edges. You doon't want to shred
-your hands when you're tinkering with things.
-
-
-****
-****
-
-There shouldn't be any hot spots (poor air
-flow).
-
-
-****
-****
-
-Sturdy card clips. Some poorly-designed cases allow cards
-to wiggle out of their slots.
-
-
-****
-****
-
-Effective and easy to use mechanisms for attaching hard
-drives, CD-ROM, CD-R/W, DVD, tape drive etc.
-
-
-****
-
-Should you buy a desktop or tower case? Our advice is go with
-tower unless you're building a no-expansions personal system and
-expect to be using the floppies a lot. Many vendors charge nothing
-extra for a tower case and the absolute maximum premium I've seen is
-$100. What you get for that is less desktop clutter, more and bigger
-bays for expansion, and often (perhaps most importantly) a beefed-up
-power-supply and fan. Putting the box and its fan under a table is
-good for maybe 5db off the effective noise level, too. Airflow is
-also an issue; if the peripheral bays are less cramped, you get better
-cooling. Be prepared to buy extension cables for your keyboard and
-monitor, though; vendors almost never include enough flex.
-
-
-
-The airflow thing is a good argument for a full- or mid-tower rather
-than the `baby tower' cases some vendors offer. However, smaller
-towers are getting more attractive as boards and devices shrink and
-more functions migrate onto the motherboard. A state of the art
-system, with all 3" disks, 300W power supply, half-size motherboard,
-on-board IDE and 64meg of RAM sockets, and half-sized expansion cards,
-will fit into a baby or midized tower with ample room for expansion;
-and the whole thing will fit under a desk and make less noise than a
-classic tower.
-
-
-
-For users with really heavy expansibility requirements,
-rackmount PC cases do exist (ask prospective vendors). Typically a
-rackmount case will have pretty much the same functionality as an
-ordinary PC case. But, you can then buy drive racks (complete with
-power supply), etc. to expand into. Also, you can buy passive
-backplanes with up to 20 or so slots. You can either put a CPU card in
-one of the slots, or connect it to an ordinary motherboard through one
-of the slots.
-
-
-
-I've recently become a big fan of Antec cases. They're inexpensive,
-sturdy, and thoughtfully engineered.
-
-----
-!!3.2. Power Supplies and Fans
-
-Power supplies can matter but quality is cheap; give preference
-to those with a Underwriter's Laboratories rating. There's some
-controversy over optimum wattage level. On the one hand, you want
-enough wattage for expansion. On the other, big supplies are noisier,
-and if you draw too little current for the rating the delivered
-voltage can become unstable. And the expected wattage load from
-peripherals is dropping steadily. On the other hand, processors
-and their cooling fans eat a lot more power than they used to.
-
-
-
-The choice is generally between 200W and 300W. After some years of
-deprecating 300W-and-up supplies, I'm now persuaded it's time to go back to
-them; a modern processor can consume 50-75W by itself, and for the newer
-dual-processor board the power supply needs to be rated 450W or up.
-
-
-
-Quality brands include PC Power and Cooling, Antec and
-Sparkle. A lot of no-name power supplies are out of spec; this
-is an area where buying a name brand is good tactics (the price premium
-won't be large).
-
-
-
-About that annoying fan noise, ask if the power-supply fan on a
-target system has a variable speed motor with thermostatic control;
-this will cut down on noise tremendously. However, be aware that a
-thermostatic sensor basically measures the temperature ''at
-the sensor'' (typically within the power supply box) and
-makes sure there is enough airflow to keep the power supply from
-overheating. The sensor does not know a thing about the temperature
-in certain hot spots likely to develop in a PC case (CPU, between
-SIMMs, between drives mounted in vertically adjacent bays).
-
-
-
-This can be a problem, because in garden variety tower cases
-there often isn't enough airflow to cool all components effectively
-even if a single fan is going at full speed. This is especially true
-if your computer has lots of add-on cards or hard disks (not much
-airflow between cards or between drives). Note that the fan in the
-power supply was basically designed to cool the power supply, not the
-components in the case. Not providing additional fans is a sign of
-cheapness. On tower PCs with "expensive" engineering (e.g. HP Vectra,
-Compaq) one will find one to two extra fans besides the one in the
-power supply.
-
-
-
-So the bottom line is, use thermostatic controls if you can to cut
-noise. But if you want high reliability, use two or more fans. Modern
-designs normally also have a small auxilliary fan mounted right over the
-chip.
-
-
-
-The noise produced by a fan is not just a function of the speed with
-which it turns. It also depends on the nature of the airflow produced by
-the fan blades and the bearings of the rotor. If the blades causes lots of
-turbulent airflow, the fan produces lots of noise. One brand of fans that
-is much more silent than most others even if going at full throttle is
-Papst.
-
-----
-!!3.3. Motherboards
-
-Provided you exercise a little prudence and stay out of the
-price basement, motherboards and BIOS chips don't vary much in
-quality. There are only six or so major brands of motherboard inside
-all those cases and they're pretty much interchangeable; brand
-premiums are low to nonexistent and cost is strictly tied to maximum
-speed and bus type. Unless you're buying from a "name" outfit like
-Compaq, Dell, or AST that rolls its own motherboards and BIOSes, there
-are only four major brands of BIOS chip (AMI, Phoenix, Mylex, Award)
-and not much to choose between 'em but the look of the self-test
-screens. One advantage Unix buyers have is that Unixes are built not
-to rely on the BIOS code (because it can't be used in protected mode
-without more pain than than it's worth). If your BIOS will boot
-properly, you're usually going to be OK.
-
-
-
-The old ``AT'' and ``Baby AT'' motherboard form factors are obsolete.
-It's an ATX world now.
-
-
-
-There are still a few potential gotchas to beware of, especially in
-the cheaper off-brand boards. One is ``shadow RAM'', a trick some
-boards use for speeding up DOS by copying the ROM contents into RAM at
-startup. It should be possible to disable this. Also, on a cacheing
-motherboard, you need to be able to disable cacheing in the memory
-areas used by expansion cards. Some cheap motherboards fail to pass
-bus-mastering tests and so are useless for use with a good SCSI
-interface; on others, the bus gets flaky when its turbo (high-speed)
-mode is on. Fortunately, these problems aren't common and are
-becoming less so.
-
-
-
-You can avoid both dangerously fossilized hardware and these
-little gotchas by sticking with a system or motherboard design that's
-been tested with Unix.
-
-
-
-Some other good features to look for in a motherboard include:
-
-
-
-
-
-
-****
-
-Gold-plated contacts in the expansion slots and RAM
-sockets. Base-metal contacts tend to grow an oxidation layer which
-can cause intermittent connection faults that look like bad RAM chips
-or boards. (This is why, if your hardware starts flaking out, one of
-the first things to do is jiggle or remove the boards and reseat them,
-and press down on the RAM chips to reseat them as well -- this may
-break up the oxidation layer. If this doesn't work, rubbing what
-contacts you can reach with a soft eraser is a good fast way to remove
-the oxidation film. Beware, some hard erasers, including many pencil
-erasers, can strip off the plating, too!)
-
-
-****
-****
-
-The board should be speed-rated as high as your
-processor, of course. It's good if it's rated higher, so upgrade to a
-faster processor is just a matter of dropping in the chip and a new
-crystal.
-
-
-****
-****
-
-Voltage, temperature and fan speed monitoring hardware.
-This is now common on motherboards based on recent iterations of the
-Intel support chips, especially those designed for server use.
-Linux supports drivers that can read this hardware, and monitoring
-can help you spot incipient board failures.
-
-
-****
-
-If you're changing a motherboard, see the
-Installing a Motherboard page first. This one even has a Linux
-note.
-
-----
-!!3.4. Memory
-
-All current PC designs include a cacheing memory controller and some
-fast on-chip cache that combine to produce higher effective speeds.
-Judging the cache design used to be one of the trickiest parts of the
-motherboard, but that stuff is all baked into the processor itself now.
-
-
-
-Current motherboards use PC100 or PC133 SDRAM, which comes packaged
-on 168 pin DIMM modules. SDRAM is a large step forward in memory speed, at
-10ns. SDRAM does not need to be installed in pairs. The key words you
-want to see on the spec sheet are:
-
-
-
-
-
-
-****
-
-SDRAM DIMM -- the physical module type.
-
-
-****
-****
-
-ECC -- support for error correcting memory, important for
-reliability; Unix makes more efficient use of hardware and thus beats
-on your memory harder than Windows does. Be sure your motherboard
-supports ECC and note that "ECC compatible" is marketing manure
-for a board that alllows you to use ECC memory but
-''doesn't'' use the ECC.
-
-
-****
-****
-
-PC100 -- this is the memory-module specification for current
-motherboards with a 100MHz Memory Bus support. This is minimum; PC133
-or PC266 is better.
-
-
-****
-****
-
-16x72 -- if it says 16x64, the extra 8 bits per 64
-needed for ECC are not present.
-
-
-****
-
-For current motherboards with 133MHz Memory Bus support, PC133 should
-be used instead of PC100; it gives 33% greater memory bandwidth at very
-little additional cost. DDR-SDRAM and RDRAM are faster memory types that
-retrieve data in chunks and give you faster throughput. So-called `PC266'
-memory is designed for motherboards that transfer at 133 but double the
-width of the front-side bus connecting processor and memory.
-
-
-
-As the throughput of processor-to-memory buses rises, memory latency
-(bus cycles required for the first fetch in a chunk) is becoming a more
-important statistic. Lower numbers are better.
-
-
-
-For more technical stuff on memory architectures, see
-The Ultimate Memory
-Guide maintained by Kingston Technologies.
-
-----
-!!3.5. Buying a Video Card
-
-Video controllers translate byte values deposited in their video
-memory by your GUI (usually an X server under Linux) into an analog
-RGB signal which drives your monitor. The simplest kinds treat their
-video memory as one big frame buffer, requiring the CPU to do all
-dot-painting. More sophisticated ``accelerated'' cards offer operations
-such as !BitBlt so your X server can hack the video memory
-algorithmically. These days almost all cards even at the low end
-actually have some acceleration features.
-
-
-
-Cards are rated by the maximum number of analog signal changes they
-can produce per second (video bandwidth). Video bandwidth can be used
-to buy varying combinations of screen resolution and refresh speed,
-depending on your monitor's capabilities.
-
-
-
-Another important variable of video cards is the size of their
-on-board video RAM. Increased memory lets you run more colors at
-higher resolutions. For instance, a 1MB card usually will only allow
-256 colors at 1024x768 while a 2MB card usually allows at least 16-bit
-color (a palette of about 65,000 colors). You'll need 4MB of video
-memory to use 24-bit or ``true'' color (16 million colors) at
-1024x768.
-
-
-
-The card's video RAM size has no effect on its speed. What does
-affect speed is the ''type'' of memory on board.
-VRAM (Video Random Access Memory) is fast but more expensive; it
-features a dual-ported design allowing two devices (the CRT controller
-and the CPU) to access the memory at the same time. DRAM (Dynamic
-Random Access Memory) is is similar to the RAM used in main memories.
-It is cheaper, more common, and slower (because the CRT controller and
-the CPU must take turns accessing the video buffer).
-
-
-
-A quick review of monitor standards:
-
-
-
-__Table 1. Monitor standards__
-
-
-!NameResolutionColorsHorizontal !FrequencyVertical FrequencyNotesMDA720x350 18.43 KHz50 HzObsoleteCGA640x200215.85 KHz60 HzObsolete320x2004EGA640x3501621.80 KHz60 HzObsoleteVGA640x4801631.50 KHz60 Hz 320x200256VESA VGA640x4801638.86 KHz72 Hz 320x200256VESA SVGA800x6001648.01 KHz72 Hz 640x4802568514/A1024x7681635.20 KHz43.5 HzObsoleteXGA640x48065536????Obsolete1024x768256VESA 1024x7681024x76825656.48 KHz70 Hz
-
-The Horizontal and Vertical Frequency columns refer to the
-monitor scan frequencies.
-
-
-
-The vertical frequency is the upper limit of the monitor's
-flicker rate; 60Hz is minimal for ergonomic comfort, 72Hz is
-VESA-recommended, and 80Hz is cutting-edge. At resolutions above VGA,
-horizontal scans take long enough that the monitor may never reach
-anywhere near the vertical-frequency maximum; how close it gets is a
-function of the horizontal-scan frequency (higher is better).
-
-
-
-For more information on how to avoid the evil screen flicker,
-see the XFree86 Video
-Timings HOWTO, a tutorial written by your humble editor
-and included with the XFree86 distribution.
-
-
-
-It's no longer possible to find MDA video boards and monitors out
-there. Anyway, prices for SVGA have collapsed so totally that it's
-wouldn't be worth bothering.
-
-
-
-XGA is an IBM-proprietary included for completeness, but is
-vanishingly rare in the clone market. 8514/A is another IBM standard
-supported by a few graphics accelerator cards. It is interlaced, and
-thus has a tendency to flicker. The VESA 1024x768 standard makes XGA
-and 8514/A obsolete.
-
-
-
-SVGA or `Super VGA' strictly refers only to 800x600 resolution,
-but is widely used for 1024x768 and even 1280x1024 resolutions.
-Standards above 1024x768 are weak and somewhat confused.
-
-
-
-These days, most vendors bundle a 15" or 17" monitor and
-super-VGA card with 1024x768 resolution in with their systems. Details to
-watch are the amount of RAM included (which will affect how much of that
-maximum resolution and how many colors you actually get), and whether the
-memory is dual-ported VRAM (slightly more expensive but much
-faster).
-
-
-
-More information on video standards is available at the
-Video Display
-Standards page of the PC Guide site.
-
-----
-!!3.6. Selecting a Monitor
-!3.6.1. What To Look For On The Spec Sheet.
-
-
-
-
-****
-
-Dot pitch of .28 or smaller on a 12"-15" monitor;
-.30 is acceptable on larger ones, especially 19" to 21" screens (but
-look extra hard at .25 21-inchers like the Viewsonic 21PS or Nokia
-445X). Dot pitch is the physical resolution of the screen's phosphor
-mask. Larger dot pitches mean that small fonts and graphic details
-will be fuzzy.
-
-
-****
-****
-
-72Hz or better vertical scan frequency, to cut
-flicker.
-
-
-****
-****
-
-Non-interlaced display. Interlacing cuts the required
-scan frequency for a given resolution in half, but makes flicker twice
-as bad. As a result, interlaced monitors are rapidly disappearing;
-don't get stuck with one.
-
-
-****
-****
-
-Does it have a tilt-and-swivel base? Adequate
-controls, including both horizontal and vertical size and horizontal
-and vertical centering? A linearity control, a trapezoidal control,
-and a color-temperature control are all pluses; the last is
-particularly important if you compose graphics on screen for hardcopy
-from a printer.
-
-
-****
-****
-
-For X use, a 14", .28mm dot pit, non-interlaced 72Mhz
-monitor at 640x480 resolution is the bare minimum for comfortable use, and
-that resolution leaves you rather squeezed for screen real estate.
-1024x768 is much better. If your budget will stand it at all, a 17"
-or 20" monitor is a good investment. A 17" monitor is minimum if
-you're going to go with 1280x1024 of 1600x1200
-resolution.
-
-
-****
-
-If you can, buy your monitor from someplace that will let you
-see the same monitor (the very unit you will walk out the door with,
-not a different or `demo' unit of the same model) that will be on your
-system. There's a lot of quality variation (even in "premium" monitor
-brands) even among monitors of the same make and model.
-
-
-
-Another good reason to see before you buy, and carry it home
-yourself, is that a lot of monitors are vulnerable to bumps. The yoke
-can get twisted, producing a disconcerting tilt in the screen
-image.
-
-
-
-The Caveat
-Emptor guide has a good section on evaluating monitor
-specifications. And there's a database of monitor specs at
-The Big Old Monitor List.
-
-----
-!3.6.2. Eric Buys A Big Monitor: Smart Shopping Tips
-
-In early 1996 the good folks at O'Reilly Associates dropped
-several $1000 checks on me in relatively quick succession (payment for
-fast-turnaround technical reviews). I decided to use the money to
-treat myself to a really good monitor.
-
-
-
-This page tells you how I did it. Specific specs and pricing
-information will date quickly, but the method should still be good
-years from now.
-
-
-
-My existing monitor wasn't bad -- a 17-inch Swan 617 that I
-could drive at a bit above 1024x768. Still, I yearned for more real
-estate -- especially vertical real estate, so I could view full
-!PostScript pages using a legible font.
-
-
-
-This brings us to our first prescription: ''be clear
-about what you want''. It's easy, and very expensive, to buy
-more monitor than you'll really use.
-
-
-
-I knew I wanted something in the 19-to-21-inch range, with
-1280x1024 or higher resolution. I knew this would probably cost me
-about $2000, and could afford it. I knew I
-''didn't'' need one of the monster projection
-monitors further upmarket, with screen sizes 24" and up. These
-will typically cost you $4K or so and are too big for desktop use
-anyway.
-
-
-
-I also knew I didn't need one of the special true-color monitors
-designed for photo composition, making print separations, and so
-forth. These creatures (always Trinitrons) have better, denser color
-than conventional tubes but at a hefty price premium (and usually at
-some cost in available resolution). If all you're going to do most of
-the time is 16 or 256-color X screens, you don't need this
-capability.
-
-
-
-Once you've settled on what you need, ''gather comparative
-data''. It was 1996, so I started out by making
-phone calls to manufacturer 800 numbers. Then I discovered that
-almost all the manufacturers had Web sites, with technical specs for
-their monitors on them. Today, you'd go to the Web first.
-
-
-
-(This space used to include detailed technical data on what I
-found " model numbers, resolutions, reviews of manufacturer
-websites, etc." but I've removed it because it's all five years
-out of data now.)
-
-
-
-This wasn't at all a hard call. The !ViewSonic 21PS and Nokia
-445X stood out from the pack immediately; their combination of high
-bandwidth with a 21-inch screen size and ultra-fine .25 dot pitch
-promised better performance than the general run of .28-pitch
-monitors.
-
-
-
-Nor was the choice between the two very hard. !ViewSonic's 21PS
-is $600 less expensive than Nokia's 445X for very similar performance.
-And, other things being equal, I'd rather buy a monitor from a
-specialist monitor manufacturer than a general consumer electronics
-outfit best known for its cellular phones.
-
-
-
-So I determined to order a !ViewSonic 21PS.
-
-
-
-This left me with a second problem. My ATI Mach 32 can't drive
-a monitor at higher than 1280x1024 resolution and 94MHz bandwidth. So
-it wouldn't be able to drive the 21PS at 1600x1200. I wound up buying
-a Mach 64.
-
-
-
-The combination worked wonderfully (two years later I discovered
-that VA Linux Systems bought the
-same monitor for its high-end systems). The only problem I have with
-it is that monitor is ''way'' bright even dialed down
-to its dimmest setting. You'll need a strong light in the room where
-you install it. Also, be aware that the only really convenient way to
-move one of these monster monitors is with a forklift!
-
-----
-!!3.7. Keyboards
-
-It's important to get a high quality keyboard with good key
-feel. See the typing-injury FAQ from sci.med.occupational to see what
-happens if you don't. Carpal tunnel syndrome is no fun for anyone,
-but it hits hackers particularly hard. Don't be a victim!
-
-
-
-Hal Snyder of Mark Williams, Co sent us the following caveat:
-"We find that about 10% of cheap no-name keyboards do not work in scan
-code set 3. We are interested in scan code set 3 because only there
-can you reprogram the keyboard on a per-key basis as to whether keys
-are make-only, make-break, or autorepeat. It is a big win for
-international support and for X."
-
-
-
-He continues: "Keytronic, Cherry, and Honeywell keyboards, as
-well as a large number of imports, work fine. My advice is to either
-buy a respected brand of keyboard, or deal with a vendor who will
-allow you to return an incompatible keyboard without charge."
-
-
-
-Allen Heim `ajh@netscape.comb writes: I'm sold on NMB
-keyboards (http://www.nmbtech.com/),
-available from Global Computer (http://www.globalcomputer.com/),
-or at (800) 8-GLOBAL. Their line of mechanical-switch keyboards now
-have a lifetime warranty, and I've just ordered my second RT-8200
-unit. I don't see it listed on their website currently, but I do see
-their "Windows 95-enhanced" model, the RT-8200W. It's the same thing,
-but with extra keys (which may be programmable; think of the Emacs
-"meta" key--could be useful).
-
-
-
-Following the wave of mid-1990s publicity about repetitive-strain
-injuries, ergonomic keyboards have become increasingly common. One that
-looks promising to your editor (though I haven't yet used it) is the
-Marquardt !MiniErgo MF2, from Marquardt Switches, Inc.; 2711 Route 20 East,
-Cazanovia NY 13035, phone (315)-655-8050; suggested list price $170,
-AT-compatible interface). Michael Scott Shappe `mshappe@jeeves.netb
-sent me a rave review of the Marquardt after having used it about six
-months.
-
-
-
-The MF2 features a conventional QWERTY layout, but with the
-right and left halves split apart and rotated about 30 degrees towards
-each other in a shallow V shape. The theory is that being able to
-angle your arms inward and your elbows out produces a less stressful
-typing position.
-
-
-
-The MF2 has no keypad, but it does have the standard 12 function
-keys across the top and arrow keys at the point of the V (meant to be
-thumb-operated).
-
-
-
-I have seen and used a device called the Maltron ergonomic
-keyboard. This keyboard splits the keys into two main groups, each
-arranged in a dished hollow. Each hand also has easy access to
-separate thumb pads of nine keys each; there is one numeric and
-arrow-key pad in the center of the unit, between the right and
-left-hand groups. Also, the keys in each group do *not* have the
-alternate-row staggering of the conventional (Scholes) keyboard; this
-subtle change reduces torsional stress on the fingers and wrists
-tremendously.
-
-
-
-I found the Maltron easy to use, and regretted having to give it
-back.
-
-
-
-For more details on many ergonomic keyboards and typing-injury
-issues in general, see Dan Wallach's FAQ on repetitive strain injuries
-and ergonomic input devices, published monthly in news.answers
-
-----
-!!3.8. Floppy Drives
-
-There's not much to be said about floppy drives. They're cheap,
-they're generic, and the rise of CD-ROM drives as a cheap distribution
-medium has made them much less important than formerly. You only ever see
-the 3.5-inch `hard-shell' floppies with 1.44MB capacity anymore.
-
-
-
-You'll probably never use floppies for anything but first boot of a
-new operating system. Bootable CD-ROMs, standard of most PCs these days,
-eliminate even that use. So go ahead and settle for cheap Mitsumi and Teac
-floppy drives. There are no `premium' floppy drives anymore. Nobody
-bothers.
-
-----
-!!3.9. Printers
-
-There's one huge gotcha about printers: ''Don't Get a `GDI'
-printer''!
-
-----
-!3.9.1. GDI printers: avoid!
-
-Low-end printer manufacturers have been increasingly moving
-towards `GDI' or `Windows' printers for their laser or LED models.
-These have the unfortunate characteristic of being, at worst, unusable
-from Unix; and at best, useable only with reduced resolution (e.g.,
-300 dpi from a 600 dpi printer).
-
-
-
-The problem is that the design of laser printers inherently
-requires that data move onto the imaging drum at a precisely-controlled
-rate, and so laser (and LED) printers have traditionally included a CPU
-of moderate speed and enough RAM to image an entire page, either as a
-complete bitmap or as ASCII, using a quick font rasterizer to form images
-on-the-fly. GDI printers, however, offload this responsibility to the
-computer, and therefore require very specialized drivers that (a) are not
-available for any Unix, AFAIK; and (b) slow down the computer a lot when
-printing is underway.
-
-
-
-Most GDI printers DO support HP's PCL in a lower resolution, so
-they can often be used from Unix via Ghostscript, but only in 300 dpi
-and/or missing some features. They may also be slower in this mode
-than in their native GDI modes. In order to print at 600 dpi with
-Ghostscript, a PCL printer must support HP's PCL at level 5e or
-better, so printer purchasers should look for that in any
-non-!PostScript model, at least at the moment. (Naturally, all of this
-could change if/when support is added to Ghostscript for more esoteric
-models; but AFAIK, this is the current set of limitations.)
-
-
-
-Finally, I've seen one extra twist on this already-twisted
-marketplace: The Brother HL-720 is advertised as supporting `PCL 5e
-for DOS' (or words to that effect). What this means is that it's a
-GDI model with a DOS driver that takes PCL 5e input and translates it
-to the printer's native GDI mode. Needless to say, this is useless
-for Unix.
-
-
-
-GDI printers are a bad design even for the DOS lemmings, because they
-slow the machine down significantly while printing is going on. Like
-`!WinModems', they're a sleazy way for manufacturers to save a few
-bucks. Our advice is, buy a printer with native Postscript and avoid
-all this crap.
-
-----
-!3.9.2. Non-GDI printers
-
-There really isn't all that much to be said about printers; the market is
-thoroughly commoditized and printer capabilities pretty much independent
-of the rest of your hardware. The PC-clone magazines will tell you what
-you need to know about print quality, speed, features, etc. The business
-users they feed on are obsessed with all these things.
-
-
-
-Most popular printers are supported by !GhostScript, and so it's easy
-to make them do !PostScript. If you're buying any letter-quality
-printer (laser or ink-jet), check to see if it's on !GhostScript's
-supported device list -- otherwise you'll have to pay a premium for
-Postscript capability! Postscript is still high-end in the MS-DOS
-market, but it's ubiquitous in the Unix world.
-
-
-
-Warning, however: if you're using ghostscript on a non-Postscript
-printer, printspeed will be slow, especially with a serial
-printer. A bitmapped 600 dpi page has a ''lot'' of pixels on
-it. Further, if you're doing much printing, ghostscript will create enormous
-spool files. (megabytes/page). At today's prices, paying the $750
-or so for Postscript capability makes sense.
-
-
-
-If you're buying a printer for home, an inkjet is a good choice
-because it doesn't use gobs of power and you won't have the
-toner/ozone/noise/etc mess that you do with a laser. If all
-you want is plain-ASCII, dot-matrix is cheaper to buy and run.
-
-
-
-Inkjets are great in that they're cheap, many of them do color, and
-there are many kinds which aren't PCL but are understood by
-Ghostscript anyway. If you print very infrequently (less than weekly,
-say), you should be careful to buy a printer whose print head gets
-replaced with every ink cartrige: infrequent use can lead to the
-drying of the ink, both in the ink cartrige and in the print head.
-The print heads you don't replace with the cartrige tend to cost
-nearly as much as the printer (~$200 for an Epson Stylus 800) once the
-warranty runs out (the third such repair, just after the warranty
-expired, totalled one informant's Stylus 800). Be careful, check
-print head replacement costs ahead of time, and run at least a
-cleaning cycle if you don't actually print anything in a given week.
-(Conversely, toner starts out dry, and ribbon ink won't evaporate for
-years...if you truly print only rarely, but neither a dot matrix nor a
-laser makes sense, consider buying no printer and taking your
-!PostScript files to a copy shop...)
-
-
-
-A parallel interface is a cheap way to make your printer
-print a lot faster than a serial line, and everyone's got a parallel port
-in their PC.
-
-
-
-A few printers for the MS-DOS market require a special
-controller card and proprietary cable to do !PostScript. These require
-MS-DOS software and typically won't run under Unix at all.
-
-
-
-Meanwhile, there are several true 600 dpi lasers that grok PCL 5e, yet
-cost less than $500 retail. Currently (December 1997) these include
-the Lexmark Optra E (and E+), the HP 5L (and 5L with suffix, and
-probably 6L), and the Brother 760. As you can't easily buy a new hard
-drive smaller than 2 gigabytes, tens of megabytes of spare space in
-/var/spool should be the accepted norm, rather than a problem, for new
-systems; I've also noticed that PCL 5e seems to include some amount of
-compression (probably RLE or font encoding) which works rather well
-for text, further reducing the spool requirements.
-
-
-
-One of our spies says good things about the Canon BJC-240 and 250. He
-reports they preint well with Ghostscript and are more reliable than
-Deskjets.
-
-
-
-I personally have a !LaserJet 6MP, and like it.
-
-----
-!!3.10. Power Protection
-!3.10.1. Overview
-
-Finally, I strongly recommend that you buy a power conditioner
-to protect your hardware. MOV-filtered power bars make nice fuses
-(they're cheap to replace), but they're not enough.
-
-
-
-The technical info in the remainder of this section is edited
-from material supplied by David E. Wexelblat
-bdwex@mtgzfs3.att.com`.
-
-
-
-There are several levels of power protection available to the
-home computer user. I break this down into 4 levels; others may have
-different ways of classifying things. The levels are:
-
-
-
-
-
-
-***#
-
-Surge Suppressor
-
-
-***#
-***#
-
-Line Conditioners
-
-
-***#
-***#
-
-Standby Power Supplies
-
-
-***#
-***#
-
-Uninterruptible Power Supplies
-
-
-***#
-
-And here's what they mean:
-
-----
-!3.10.2. Surge suppressors
-
-These are basically a fancy fuse between the source and your
-hardware; they clamp down spikes, but can't fill in a low voltage
-level or dropout.
-
-
-
-This is a bare minimum level of protection that any piece of
-expensive electronics should have. Note that this applies to more
-than just AC power; surge suppressors are available for (and should be
-used on) phone lines, and RS-232 and parallel connections (for use on
-long lines; generally not needed if the devices is colocated with the
-computer and all devices are protected from outside sources). Note
-also that ''all'' devices connected to your computer
-need to be protected; if you put a surge suppressor on your computer
-but not your printer, then a zap on the printer may take out the
-computer, too.
-
-
-
-An important fact about surge suppressors is that ''they
-need to be replaced if they absorb a large surge''. Besides
-fuses, most suppressors rely on on components called Metal-Oxide
-Varistors (or MOVs) for spike suppression, which degrade when they
-take a voltage hit. The problem with cheap suppressors is that they
-don't tell you when the MOV is cooked, so you can end up with no spike
-protection and a false sense of security. Better ones have an
-indicator.
-
-
-
-You can buy surge suppressors at any Radio Shack; for better prices, go
-mail-order through Computer Shopper or some similar magazine. All of
-these are low-cost devices ($10-50).
-
-----
-!3.10.3. Line Conditioners
-
-These devices filter noise out of AC lines. Noise can degrade
-your power supply and cause it to fail prematurely. They also protect
-against short voltage dropouts and include surge suppression.
-
-
-
-My Tripp-Lite 1200 was typical of the better class of line
-conditioners; a box with a good big soft-iron transformer and a
-couple of moby capacitors in it and ''no'' conductive
-path between the in and out sides. With one of these, you can laugh
-at brownouts and electrical storms. You can get for $139 or so by mail
-order. A fringe benefit of this little beauty is that if you
-accidentally pull your plug out of the wall you may find you actually
-have time to re-connect it before the machine notices (I did this
-once). But a true SPS or UPS is better.
-
-
-
-Netter Trey !McLendon has good things to say about Zero Surge
-conditioners. He says: "Our systems at work
[[...
] have been
-protected for 2.5 years now through many a violent storm...one strike
-knocked [[out] the MOV-type suppressors on a Mac dealer's training
-setup across the street from us. The Zero Surge just sort of buzzed
-when the surge came in, with no interruption whatsoever. The basic
-principle is this: ZS units slow down the surge with a network of
-passive elements and then sends it back out the neutral line, which is
-tied to ground _outside at the box_ by code. MOV units shunt the
-surge to ground _at the computer_, where it leaps across serial ports,
-network connections, etc. doing its deadly work."
-
-
-
-Price vary widely, from $40-400, depending on the power rating
-and capabilities of the device. Mail-order from a reputable supply
-house is your best bet. Line conditioners typically
-''don't'' need to be replaced after a surge; check to
-see if yours includes MOVs.
-
-----
-!3.10.4. Standby power supplies (SPSs)
-
-These devices are battery-based emergency power supplies that
-provide power for your system via an inverter if the power fails. An
-SPS will generally have all the capabilities of a line conditioner as
-well.
-
-
-
-Note: these devices do not come on line until after the power
-fails, and have a certain amount of delay (typically some
-milliseconds) before they come on line. If the capacitors in your
-power supply are not large enough, the SPS may not cut in soon enough
-to prevent your computer from seeing the power failure.
-
-
-
-Note also that many SPSs are marketed as Uninterruptable Power
-Supplies (see below). This is incorrect. Any device with a non-zero
-cutover time cannot be a true UPS. If the ad mentions a cutover time,
-it's an SPS, and not a UPS.
-
-
-
-The price range for these devices (increasing with increasing
-peak load capacity and with decreasing cutover time) is $200-2000. An
-SPS will ''not'' need to be replaced after absorbing
-a large surge.
-
-----
-!3.10.5. Uninterruptable power supplies (UPSs)
-
-These devices provide full-time isolation from the incoming AC
-line through a transformer of some sort. These devices are on-line at
-all times, and if the AC line fails, the batteries will cut in. Your
-devices will see no interruption of their incoming AC. UPSs cost
-more, and provide more features. They are the ultimate in power
-protection. Many UPSs have an intelligent interface that will notify
-a connected device of a power failure, allowing it to shut down
-cleanly. UPSs also provide the capabilities of a line
-conditioner. The price range (for devices in the size range for a home
-computer) are $200-$1500. An UPS will ''not'' need
-to be replaced after absorbing a large surge.
-
-
-
-Now, given this information, how does one decide what to get?
-For a system that runs unattended, like most Unix systems, it is best
-to have a device that provides both power holdover and a power failure
-signal. Hence, for a Unix system, a UPS or SPS with Unix monitoring
-software is the best choice.
-
-
-
-If the vendor isn't secretive about interface specs, it's fairly
-simple to write your own daemon to monitor a serial port, and send
-init a SIGPWR signal when it sees a powerdown notification on the
-port. Freeware power-monitor demons are available for Linux.
-
-
-
-Many UPS/SPS signal ports work by asserting a pin, so that one
-could use a modem-control serial port on the PC and wire this pin to
-"Carrier Detect" in order to monitor it. Some, like the APC "SmartUPS"
-series, actually conduct an ASCII dialog with the host through a serial line
-in order to accomplish the monitor functions.
-
-
-
-Our recommendation for a production Unix environment is a
-configuration like the following:
-
-
-
-
-
-
-***#
-
-An on-line UPS or SPS for the computer system. An intelligent
-interface is mandatory, along with appropriate software for
-ordered shutdown.
-
-
-***#
-***#
-
-Surge suppression on all phone lines, and also on serial/parallel
-lines that leave the room.
-
-
-***#
-***#
-
-Line conditioners on any devices not connected to the UPS. If
-you do take a power hit, it's cheaper to replace a $50 line
-conditioner than a $1500 laser printer.
-
-
-***#
-
-If this is too expensive for you, then downgrade the UPS/SPS to
-a line conditioner like the !TrippLite. But don't go without at least
-that. Running unprotected is false economy, because you
-''will'' lose equipment to electrical storms -
-and, Murphy's Law being what it is, you will always get hit at the
-worst possible time.
-
-
-
-An important question is "How do I know how big a UPS/SPS to
-get?" The watt rating of the UPS/SPS should be at least the sum of
-the peak ratings off all equipment connected to it (don't forget the
-console monitor). Power-supply marketroids tend to quote you
-capacities and formulas like "sum of VA ratings + 20%" which
-(surprise!) push you towards costlier hardware. Ignore them. If a
-watt rating is not given, watts = .75*VAmax.
-
-
-
-One other consideration is that you typically shouldn't put a
-laser printer on a UPS - toner heaters draw enough current to
-overload a UPS and cause a shutdown within seconds. The other thing
-is that you can't even put the laser printer on the same circuit with
-a UPS - the heater kicks on every 20-30 seconds, and most UPSs
-will see the current draw as a brownout. So buy a separate line
-conditioner for the laser printer.
-
-
-
-Finally, read the UPS's installation manual carefully if you're going
-to use it with other power-protection devices. Some UPSs don't like having
-surge suppressors between them and the equipment.
-
-
-
-David personally recommends surge suppressors and line conditioners from
-Tripp-Lite (available both mail-order and retail), and UPSs from Best Power
-Technologies (Necedah, WI - 1-(800)-356-5737). I can enthusiastically second
-the !TrippLite recommendation, but haven't dealt with Best Power at all.
-
-
-
-Tripp-Lite has a whole range of products, from a $10 phone-line
-surge-suppressor, to line conditioners and SPSs with prces in the hundreds of
-dollars. They have a line of $50-80 line conditioners that are good for most
-peripherals (including your home stereo :-b).
-
-
-
-Best Power Technologies sells two lines of UPSs in the range for
-home systems. The older and more expensive FERRUPS line (which is
-what David has) has a smart interface, and very good filtering and
-surge-suppression capabilities. He says "I have a 1.15kVA FERRUPS for
-my home system, which is overkill with my current hardware (although
-it rode out a 45 minute power failure with nary a whisper - no
-reboot). In 1990, I paid ~$1600 for this device, and that has since
-gone up. They also sell a newer line of Fortress UPSs. These are
-better suited in price for home systems. I don't know much about
-them, as they were not available when I bought my UPS. I expect that
-this is what most people will want to consider, though. In addition,
-Best sells Check-UPS, a software package (in source form) for
-monitoring the UPS and shutting it down. I have found Best to be a
-good company to deal with, with competent, knowledgeable sales people
-(who will be able to help you pick the right device), and helpful,
-courteous, and responsive technical support."
-
-
-
-Other things to know:
-
-
-
-A UPS should be wired directly to (or plugged directly into) the
-AC supply (i.e. a surge suppressor is neither required nor suggested
-between the wall and the UPS). In addition, a surge suppressor
-between the UPS and the equipment connected to it is redundant.
-
-----
-!!3.11. Radio Frequency Interference
-
-(Thanks to Robert Corbett `Robert.Corbett@Eng.Sun.COMb for
-contributing much of this section)
-
-
-
-Radio Frequency Interference (RFI) is a growing problem with
-PC-class machines. Today's processor speeds (above 33MHz) are such
-that the electromagnetic noise generated by a PC's circuitry in normal
-operation can degrade or jam radio and TV reception in the
-neighborhood. Such noise is called Radio Frequency Interference
-(RFI). Computers, as transmitting devices, are regulated by the
-Federal Communications Commission (FCC).
-
-
-
-FCC regulations recognize two classes of computer:
-
-
-
-If a PC is to be used in a home or apartment, it must be
-certified to be FCC class B. If it is not, neighbors have a legal
-right to prevent its use. FCC class A equipment is allowed in
-industrial environments.
-
-
-
-Many systems are not FCC class B. Some manufacturers build
-boxes that are class B and then ship them with class A monitors or
-external disk drives. Even the cables can be a source of RFI.
-
-
-
-It pays to be cautious. For example, the Mag MX17F is FCC class
-B. There are less expensive versions of the MX17 that are not. The
-Mag MX17 is a great monitor (I wish I had one). It would be painful
-to own one and not be allowed to use it.
-
-
-
-An upgradeable system poses special problems. A system that is
-FCC class B with a 33 MHz CPU might not be when the CPU is upgraded to
-a 50 or 66 MHz CPU. Some upgrades require knockouts in the case to be
-removed. If a knockout is larger than whatever replaces it, RFI can
-leak out through the gap. Grounded metal shims can eliminate the
-leaks.
-
-
-
-Even Class B systems don't mix well with wireless phonesets (not cellular
-phones, but the kind with a base station and antennaed headset). You'll often
-find a wireless phone hard to use withing 20 feet of a Class B machine.
-
-
-
-To cut down on RFI, get a good metal case with tight joints, or at
-least make sure any plastic one you buy has a conductive lining. You
-can also strip the painted metal-to-metal contacting parts of paint so
-that there's good conductive metal contact. Paint's a poor conductor
-in most cases, so you can get some benefit from this.
-
-----
-!!!4. Performance Tuning
-
-Here are the places where you can trade off spending against the
-performance level you want to buy and your expected job mix.
-
-----
-!!4.1. How To Pick Your Processor
-
-Right now (mid-2001), the chips to consider for running Unix are the
-Pentium IIs and Pentium IIIs and their clone equivalents from AMD or
-Cyrix. The Pentium IV is something of a dog (very poor price-performance,
-actually slower than a III on some benchmarks), and the Itanium isn't
-out of the starting gate.
-
-
-
-Brands don't matter much, so don't feel you need to pay Intel's
-premiums if you see an attractive Cyrix, AMD or other chip-clone
-system offered.
-
-
-
-To compare the performance of different Intel-based systems with
-each other and with machines from other manufacturers, you can take a
-look at the SPECmark Table at ftp://ftp.cdf.toronto.edu/pub/spectable.
-That document recommends (and I do too) that you read the SPEC FAQ at
-http://www.specbench.org/spec/specfaq.html
-to get background before browsing the table.
-
-
-
-Good current advice about chipsets can be found at
-The Cheap /Linux/ Box.
-
-----
-!!4.2. Of Memory In...
-
-Buy lots of RAM, it's the cheapest way to improve real performance on
-any virtual-memory system. 64MB now comes standard on most
-clone configurations. This is good enough for X.
-
-
-
-Tuning is simple. Watch your job mix with top(1) and add memory until
-you're not swapping to disk any more.
-
-----
-!!4.3. Bus Wars
-
-This is yet another area in which progress has simplified your
-choices a lot. There used to be no fewer than four competing bus
-standards out there (ISA, EISA, VESA/VLB, PCI, and PCMCIA). Now there
-are effectively just two -- PCI for desktop/tower machines and PCMCIA
-for laptops.
-
-----
-!4.3.1. Bus Types
-
-PCI is Intel's fast 64-bit bus for the Pentium. Many PCI boards
-are actually PCI/ISA that supports both standards, so you can use less
-expensive ISA peripherals and controllers. The tradeoff is that dual-bus
-boards lose about 10% of their performance relative to single-bus PCI
-boards.
-
-
-
-I used to recommend these dual-bus boards, but no longer do. The
-on-board USB support and PS/2 mouse port now common on motherboards made
-the difference, it means you no longer need ISA even internally (and PCI
-cards are cheap these days). For your desktop machine, go PCI-only.
-
-
-
-Try to find a motherboard that drives the PCI bus at 66MHz rather
-than the more typical 33MHz. But that's a minor issue nowadays; the
-peripherals that dump really large volumes of data (disks, graphics cards)
-will do direct-memory access or have their own dedicated high-speed bus
-(like AGP).
-
-
-
-In the laptop market everything is PCMCIA. PCMCIA peripherals are
-about the size of credit cards (85x54mm) and vary in thickness between
-5 and 10mm. They have the interesting feature that they can be
-hot-swapped (unplugged out and plugged in) while the computer is on.
-However, they are seldom seen in desktop machines. They require a
-special daemon to handle swapping, which is now standard under
-Linux.
-
-----
-!!4.4. Disk Wars: IDE vs. SCSI
-!4.4.1. Overview
-
-Another basic decision is IDE vs. SCSI. Either kind of disk
-costs about the same, but the premium for a SCSI card varies all over
-the lot, partly because of price differences between VLB and PCI SCSI
-cards and especially because many motherboard vendors bundle an IDE
-chipset right on the system board. SCSI gives you better speed and
-throughput and loads the processor less, a win for larger disks and an
-especially significant consideration in a multi-user environment; also
-it's more expandable.
-
-
-
-In terms of pure disk speed, IDE will always be faster, as they use
-the same underlying disks, and IDE has less overhead. As fast as disks
-are getting today, the difference is effectively noise. The real
-advantage of SCSI comes from its extra brains. IDE uses polled I/O,
-which means that when you are accessing the disk, the CPU isn't doing
-anything else. Most SCSI systems, on the other hand, are DMA based,
-freeing up the system to do other things at the same time. Hence, in
-terms of full system performance, SCSI is indeed faster if you have
-good hardware and an intelligent OS.
-
-
-
-Another important win for SCSI is that it handles multiple devices
-much more efficiently. You can have at most two IDE devices; four
-for EIDE. SCSI permits up to 7 (15 for wide SCSI).
-
-
-
-If you have two IDE drives, only one can transfer between memory and
-disk at once. In fact, you have to program them at such a low level that
-one drive might actually be blocked from ''seeking'' while
-you're talking to the other drive. SCSI drives are mostly autonomous and
-can do everything at once; and current SCSI drives are not quite fast
-enough to flood more than half the SCSI bus bandwidth, so you can have at
-least two drives on a single bus pumping full speed without using it up.
-In reality, you don't keep drives running full speed all the time, so you
-should be able to have 3-4 drives on a bus before you really start feeling
-bandwidth crunch.
-
-
-
-Of course, IDE is cheaper. Many motherboards have IDE right on board
-now; if not, you'll pay maybe $15 for an IDE adapter board, as opposed
-to $200+ for the leading SCSI controller. Also, the cheap SCSI
-cabling most vendors ship can be flaky. You have to use expensive
-high-class cables for consistently good results. See Mark Sutton's horror story.
-
-----
-!4.4.2. Enhanced IDE
-
-These days you seldom see plain IDE; souped-up variants are more
-usual. These are "Enhanced IDE" (E-IDE) and "Fast AT Attachment"
-(usually ATA for short). ATA is Seagate's subset of E-IDE, excluding
-some features designed to permit chaining with CD-ROMs and tape drives
-using the new "ATAPI" interface (an E-IDE extension; so far only the
-CD-ROMs exist); in practice, ATA and E-IDE are identical.
-
-
-
-You'll need to be careful about chaining in CD-ROMs and tape
-drives when using IDE/ATA. The IDE bus sends all commands to all
-disks; they're supposed to latch, and each drive then checks to see
-whether it is the intended target. The problem is that badly-written
-drivers for CD-ROMs and tapes can collide with the disk command set.
-It takes expertise to match these peripherals.
-
-
-
-Neither ATA nor E-IDE has the sustained throughput capacity of
-SCSI (they're not designed to) but they are 60-90% faster than plain
-old IDE. E-IDE's new ``mode 3'' boosts the IDE transfer rate from
-IDE's 3.3MB/sec to 13.3MB/sec. The new interface supports up to 4
-drives of up to 8.4 gigabytes capacity.
-
-
-
-E-IDE and ATA are advertised as being completely compatible with
-old IDE. Theoretically, you can mix IDE, E-IDE and ATA drives and
-controllers any way you like, and the worst result you'll get is
-conventional IDE performance if the enhancements don't match up (the
-controller picks the lowest latch speed). In practice, some IDE
-controllers (notably the !BusLogic) choke on enhanced IDE.
-
-
-
-Accordingly, I recommend against trying to mix device types an
-an E-IDE/ATA bus. Unfortunately, this removes much of E-IDE/ATA's
-usefulness!
-
-
-
-E-IDE on drives above 540MB does automatic block mapping to fool the
-BIOS about the drive geometry (avoiding limits in the BIOS type tables).
-They don't require special Unix drivers.
-
-
-
-Many motherboards now support ``dual EIDE'' channels, i.e. two separate
-[[E]IDE interfaces each of which can, theoretically, support two IDE
-disks or ATA-style devices.
-
-----
-!4.4.3. SCSI Terminology
-
-The following, by Ashok Singhal
-`ashoks@duckjibe.eng.sun.comb of Sun Microsystems with additions
-by your humble editor, is a valiant attempt to demystify SCSI
-terminology.
-
-
-
-The terms ``SCSI'', ``SCSI-2'', and ``SCSI-3'' refer to three different
-specifications. Each specification has a number of options. Many of these
-options are independent of each other. I like to think of the main options
-(there are others that I'll skip over because I don't know enough about them to
-talk about them on the net) by classifying them into five categories:
-
-----__4.4.3.1. Logical: SCSI-1, SCSI-2, SCSI-3__
-
-This refers to the commands that the controllers understand. You'll
-no longer see SCSI-1 in new hardware. SCSI-3 is a superset of SCSI-2
-including commands intended for CD-R and streaming multimedia
-devices.
-
-----__4.4.3.2. Electrical Interface__
-
-
-
-
-****
-
-single-ended (max cable length 6 meters)
-
-
-****
-****
-
-differential (max cable length 25 meters)
-
-
-****
-
-This option is independent of command set, speed, and path width.
-Differential is less common but allows higher transfer speeds, better noise
-immunity and longer cables. It's rare in SCSI-1 controllers.
-
-
-
-You will normally see single-ended SCSI controllers on
-low-speed devices such as tapes and CD drives, and differential
-SCSI on hard drives (look for the specification LVD which means
-"low-voltage differential").
-
-
-
-Nowadays most controllers support both electrical interfaces, but if
-you mix LVD with single-ended on the same chain, the whole chain will fall
-back to single-ended (and possibly halve the speed of the faster
-devices).
-
-----__4.4.3.3. Handshake__
-
-
-
-
-****
-
-Asynchronous (acknowledge each word (8, 16 or 32 bits) transferred.
-
-
-****
-****
-
-Synchronous (multiple-word transfers permitted between ACKS).
-
-
-****
-
-Synchronous is faster. This mode is negotiated between controller
-and device; modes may be mixed on the same bus. This is independent
-of command set, data width, and electrical interface.
-
-----__4.4.3.4. Synchronous Speed (does not apply for asynchronous option)__
-
-Normal transfer speed is 5 megabytes/sec. The ``fast'' option
-(10 mb/sec) is defined only in SCSI-2 and SCSI-3. Fast-20 (or
-``Ultra'') is 20 mb/sec; Fast-40 (or "Ultra-2") is 40MB/sec. The fast
-options basically defines shorter timing parameters such as the
-assertion period and hold time.
-
-
-
-The parameters of the synchronous transfer are negotiated
-between each target and initiator so different speed transfers
-can occur over the same bus.
-
-----__4.4.3.5. Path width__
-
-The standard SCSI data path is 8 bits wide. The ``wide'' option
-exploits a 16- or 32-bit data path (uses 68-pin rather than 50-pin
-data cables). You also get 4-bit rather than 3-bit device IDs, so you
-can have up to 16 devices. The wide option doubles or quadruples your
-transfer rate, so for example a fast-20/wide SCSI link using 16 bits
-transfers 40mb/sec.
-
-
-
-What are those ``LUN'' numbers you see when you boot up? Think
-of them as sub-addresses on the SCSI bus. Most SCSI devices have only
-one ``logical'' device inside them, thus they're LUN zero. Some SCSI
-devices can, however, present more than one separate logical unit to
-the bus master, with different LUNs (0 through 7). The only context
-in which you'll normally use LUNs is with CD-ROM juke boxes. Some
-have been marketed that offer up to 7 CD-ROMS with one read
-head. These use the LUN to differentiate which disk to select.
-
-
-
-(There's history behind this. Back in the days of EISA, drives were
-supposed to be under the control of a separate SCSI controller, which
-could handle up to 7 such devices (15 for wide SCSI). These drives
-were to be the Logical Units; hence the LUN, or Logical Unit Number.
-Then, up to 7 of these SCSI controllers would be run by the controller
-that we today consider the SCSI controller. In practice, hardware
-cost dropped so rapidly, and capability increased so rapidly, it
-became more logical to embed the controller on the drive.)
-
-----
-!4.4.4. Avoiding Pitfalls
-
-Here are a couple of rules and heuristics to follow:
-
-
-
-Rule 1: Total SCSI cable length (both external and internal devices) must
-not exceed six meters. For modern Ultra SCSI (with its higher speed)
-cut that to three feet!
-
-
-
-It's probably not a good idea to cable 20MB/s or faster SCSI devices
-externally at all. If you must, one of our informants advises using a
-Granite Digital ``perfect impedance'' teflon cable (or equivalent);
-these cables basically provide a near-perfect electrical environment
-for a decent price, and can be ordered in custom configurations if
-needed.
-
-
-
-A common error is to forget the length of the ribbon cable used
-for internal devices when adding external ones (that is, devices
-chained to the SCSI board's external connector).
-
-
-
-Rule 2: Both ends of the bus have to be electrically terminated.
-
-
-
-On older devices this is done with removable resistor packs
-- typically 8-pin-inline widgets, yellow or blue, that are
-plugged into a plastic connector somewhere near the edge of the PCB
-board on your device. Peripherals commonly come with resistor packs
-plugged in; you must ''remove'' the packs on all
-devices except the two end ones in the physical chain.
-
-
-
-Newer devices advertised as having "internal termination" have a
-jumper or switch on the PCB board that enables termination. These
-devices are preferable, because the resistor packs are easy to lose or
-damage.
-
-
-
-Rule 3: No more than seven devices per chain (fifteen for Wide
-SCSI).
-
-
-
-There are eight SCSI IDs per controller. The controller reserves ID 7
-or 15, so your devices can use IDs 0 through 6 (or 0 through 14,
-wide). No two devices can share an ID; if this happens by accident,
-neither will work.
-
-
-
-The conventional ID assignments are: Primary hard disk = ID ,
-Secondary hard disk = ID 1, Tape = ID 2. Some Unixes (notably SCO)
-have these wired in. You select a device's ID with jumpers on the PCB
-or a thumbwheel.
-
-
-
-SCSI IDs are completely independent of physical device chain
-position.
-
-
-
-Heuristic 1: If you're buying narrow SCSI, stick with controllers and
-devices that use the Centronics-style 50-pin connector. Internally these
-connectors are physically identical to diskette cables. Externally they
-use a D50 shell. This "standard" connector is common in the
-desktop/tower/rackmount-PC world, but you'll find lots of funky DIN and
-mini-DIN plugs on devices designed for Macintosh boxes and some laptops.
-Ask in advance and don't get burned.
-
-
-
-Heuristic 2: For now, when buying a controller, go with an Adaptec
-xx42 or one of its clones such as the !BusLogic 542. (I like the
-!BusLogic 946 and 956, two particularly fast Adaptec clones
-well-supported under Linux.) The Adaptec is the card everybody
-supports and the de-facto standard. Occasional integration problems
-have been reported with Unix under Future Domain and !UltraStor cards,
-apparently due to command-set incompatibilities. At least, before you
-buy these, make sure your OS explicitly supports them.
-
-
-
-However: Beware the combination of an Adaptec 1542 with a PCI Mach32
-video card. Older (1.1) Linux kernels handled it OK, but all current ones
-choke. Your editor had to replace his 1542 because of this, swearing
-sulphurously the while.
-
-
-
-Heuristic 3: You'll have fewer hassles if all your cables are made by
-the same outfit. (This is due to impedence reflections from minor
-mismatches. You can get situations where cable A will work with B,
-cable B will work with C, but A and C aren't happy together. It's
-also non-commutative. The fact that `computer to A to B' works
-doesn't mean that `computer to B to A' will work.
-
-
-
-Heuristic 4. Beware Cheap SCSI Cables!
-
-
-
-Mark Sutton tells the following instructive horror story in a
-note dated 5 Apr 1997:
-
-
-
-I recently added an additional SCSI hard drive to my home
-machine. I bought an OEM packaged Quantum Fireball 2 gig SCSI drive
-(meaning, I bought a drive in shrinkwrap, without so much as mounting
-hardware or a manual. Thank God for Quantum's web page or I would
-have had no idea how to disable termination or set the SCSI ID on this
-sucker. Anyway, I digress...). I stuck the drive in an external
-mounting kit that I found in a pile of discarded computer parts at
-work and my that boss said I could have. (All 5 of my internal bays
-were full of devices.)
-
-
-
-Anyway, I had my drive, and my external SCSI mounting kit, I
-needed a cable.
-
-
-
-I went into my friendly local CompUSA in search of a SCSI cable,
-and side-by-side, on two hooks, were two "identical" SCSI cables.
-Both were 3 feet. Both had Centronics to Centronics connectors, both
-were made by the same manufacturer. They had slightly different model
-numbers. One was $16.00, one was $30.00. Of course, I bought the $16
-cable.
-
-
-
-Bad, I say, ''bad bad mistake''. I hooked this
-sucker up like so:
-
-
- ---- --- ----- ---
-|Internal|--|Adaptec|-|New Quantum|-|UMAX |
-|Devices | |1542CF | ^ | Disk | ^ |Scanner|
----- ---- | ----- | ---
-| |
-New $16 cable Cable that came
-with scanner.
-
-Shortly after booting, I found that data all over my old internal hard
-drive was being hosed. This was happening in DOS as well as in Linux.
-Any disk access on either disk was hosing data on both disks, attempts
-to scan were resulting in corrupted scans *and* hosing files on the
-hard disks. By the time I finished swapping cables around, and
-checking terminations and settings, I had to restore both Linux and
-DOS from backups.
-
-
-
-I went back to CompUSA, exchanged the $16 cable for the $30 one, hooked
-it up and had no more problems.
-
-
-
-I carefully examined the cables and discovered that the $30 cable
-contained 24 individual twisted pairs. Each data line was twisted
-with a ground line. The $16 cable was 24 data wires with one overall
-grounded shield. Yet, both of these cables (from the same
-''manufacturer'') were being sold as SCSI cables!
-
-
-
-You get what you pay for.
-
-
-
-(Another correspondent guesses that the cheap cable probably
-said ``Macintosh'' on it. The Mac connector is missing most of its
-ground pins.)
-
-----
-!4.4.5. Trends to Watch For
-
-Disks of less than 10GB capacity simply aren't being manufactured
-anymore; there's no margin in them. Our spies tell us that all major disk
-makers retooled their lines a while back to produce 9GB unit platters (IBM
-is an exception; it seems to use 6GB platters), which are simply being
-stacked 2N per spindle to produce ranges of drives with roughly 18GB
-increments of capacity.
-
-
-
-Average drive latency is inversely proportional to the disk's
-rotational speed. For years, most disks spun at 3600 rpm; most disks now
-spin at 7,200 rpm, and high-end disks like the Seagate Cheetah line are
-moving to 10,000 and 15,000 rpm. These fast-spin disks run extremely hot;
-expect cooling to become a critical constraint in drive design.
-
-
-
-Drive densities have reached the point at which standard inductive
-read/write heads are a bottleneck. In newer designs, expect to
-see magnetoresistive head assemblies with separate read and write
-elements.
-
-----
-!4.4.6. More Resources
-
-There's a USENET
-SCSI FAQ. Also see the home page of the
-T10
-committee that writes SCSI standards.
-
-
-
-There is a large searchable database of hard disk and controller
-information at the PC DISK
-Hardware Database.
-
-----
-!!4.5. Other Disk Decisions
-
-Look at seek times and transfer rates for your disk; under Unix
-disk speed and throughput are so important that a 1-millisecond
-difference in average seek time can be quite noticeable.
-
-----
-!4.5.1. Disk Brands
-
-An industry insider (a man who buys hard drives for systems
-integration) has passed us some interesting tips about drive brands.
-He says the absolute best-quality drives are the Hewlett-Packards but
-you will pay a hefty premium for that quality.
-
-
-
-The other top-tier manufacturers are IBM, Quantum and Seagate; these
-drives combine cutting-edge technology with very aggressive pricing.
-
-
-
-The second tier consists of Maxtor, Conner, and Western Digital.
-
-
-
-Maxtor often leads in capacity and speed, but at some cost in
-other quality measures. For example, many of the high-capacity Maxtor
-drives have serious RFI emission problems which can cause high error
-rates. SCSI has built-in ECC correction, so SCSI drives only take a
-performance hit from this; but it can lead to actual errors from IDE
-drives.
-
-
-
-Western Digital sells most of its output to Gateway at
-sweetheart prices; WD drives are thus not widely available
-elsewhere.
-
-
-
-The third tier consists of Fujitsu, Toshiba, and everyone else. My
-friend observes that the Japanese, despite their reputation for process
-engineering savvy, are notably poor at drive manufacturing; they've never spent
-the money and engineering time needed to get really good at making the
-media.
-
-
-
-Just as a matter of interest, he also says that hard drives
-typically start their life cycle at an OEM price around $400 each.
-When the price erodes to around $180, the product gets turfed -
-there's no margin any more.
-
-
-
-I've found a good cheap source for reconditioned SCSI disks at
-Uptime Computer
-Support Services.
-
-----
-!!4.6. Tuning Your I/O Subsystem
-
-''(This section comes to us courtesy of Perry The Cynic,
-`perry@sutr.cynic.orgb; it was written in 1998. My own experience
-agrees pretty completely with his. I have revised the numbers in it since
-to reflect more recent developments.)''
-
-
-
-Building a good I/O subsystem boils down to two major points:
-''pick matched components'' so you don't over-build any
-piece without benefit, and ''construct the whole pipe such that
-it can feed what your OS/application combo needs''.
-
-
-
-It's important to recognize that ``balance'' is with respect to not only
-a particular processor/memory subsystem, but also to a particular OS
-and application mix. A Unix server machine running the whole TCP/IP server
-suite has radically different I/O requirements than a video-editing
-workstation. For the ``big boys'' a good consultant will sample the I/O mix
-(by reading existing system performance logs or taking new measurements)
-and figure out how big the I/O system needs to be to satisfy that app
-mix. This is not something your typical Linux buyer will want to do;
-for one, the application mix is not static and will change over time. So what
-you'll do instead is design an I/O subsystem that is internally
-matched and provides maximum potential I/O performance for the money
-you're willing to spend. Then you look at the price points and compare
-them with those for the memory subsystem. That's the most important
-trade-off inside the box.
-
-
-
-So the job now is to design and buy an I/O subsystem that is well matched
-to provide the best bang for your buck. The two major performance numbers
-for disk I/O are latency and bandwidth. Latency is how long a program
-has to wait to get a little piece of random data it asked for.
-Bandwidth is how much contiguous data can be sent to/from the disk
-once you've done the first piece. Latency is measured in milliseconds (ms);
-bandwidth in megabytes per second (MB/s). Obviously, a third number of interest
-is how big all of your disks are together (how much storage you've got),
-in Gigabytes (GB).
-
-
-
-Within a rather big envelope, minimizing latency is the cat's meow.
-Every millisecond you shave off effective latency will make your system
-feel significantly faster. Bandwidth, on the other hand, only helps you
-if you suck a big chunk of contiguous data off the disk, which happens
-rarely to most programs. You have to keep bandwidth in mind to avoid
-mis-matching pieces, because (obviously) the lowest usable bandwidth in
-a pipe constrains everything else.
-
-
-
-I'm going to ignore IDE. IDE is no good for multi-processing systems,
-period. You may use an IDE CD-ROM if you don't care about its
-performance, but if you care about your I/O performance, go SCSI.
-
-
-
-Let's look at the disks first. Whenever you seriously look at a
-disk, ''get its data sheet''. Every reputable
-manufacturer has them on their website; just read off the product code
-and follow the bouncing lights. Beware of numbers (``12ms fast!')
-you may see in ads; these folks often look for the lowest/highest
-numbers on the data sheet and stick them into the ad copy. Not
-dishonest (usually), but ignorant.
-
-
-
-What you need to find out for a disk is:
-
-
-
-
-
-
-***#
-
-What kind of SCSI interface does it have? Look for
-"fast", "ultra", and "wide". Ignore disks that say "fiber"
-(this is a specialty physical layer not appropriate for the insides
-of small computers). Note that you'll often find the same disk with
-different interfaces.
-
-
-***#
-***#
-
-What is the "typical seek" time (ms)? Make sure
-you get "typical", not "track-to-track" or "maximum" or some other
-measure (these don't relate in obvious ways, due to things like
-head-settling time).
-
-
-***#
-***#
-
-What is the rotational speed? This is typically
-4500, 5400, 7200, 10000, or 15000 rpm (rotations per minute). Also look
-for "rotational latency" (in ms). (In a pinch, average rotational
-latency is approx. 30000/rpm in milliseconds.)
-
-
-***#
-***#
-
-What is the `media transfer rate' or speed (in
-MB/s)? Many disks will have a range of numbers (say,
-7.2-10.8MB/s). Don't confuse this with the "interface transfer
-rate" which is always a round number (10 or 20 or 40MB/s) and is
-the speed of the SCSI bus itself.
-
-
-***#
-
-These numbers will let you do apple-with-apples comparisons of disks.
-Beware that they will differ on different-size models of the same disk;
-typically, bigger disks have slower seek times.
-
-
-
-Now what does it all mean? Bandwidth first: the `media transfer rate'
-is how much data you can, under ideal conditions, get off the disk per
-second. This is a function mostly of rotation speed; the faster the
-disk rotates, the more data passes under the heads per time unit. This
-constrains the sustained bandwidth of ''this disk''.
-
-
-
-More interestingly, your effective latency is the sum of typical seek
-time and rotational latency. So for a disk with 8.5ms seek time and 4ms
-rotational latency, you can expect to spend about 12.5ms between the
-moment the disk `wants' to read your data and the moment when it
-actually starts reading it. This is the one number you are trying to
-make small. Thus, you're looking for a disk with low seek times and
-high rotation (RPM) rates.
-
-
-
-For comparison purposes, the first hard drive I ever bought was a 20MB
-drive with 65ms seek time and about 3000RPM rotation. A floppy drive
-has about 100-200ms seek time. A CD-ROM drive can be anywhere between
-120ms (fast) and 400ms (slow). The best IDE harddrives have about
-10-12ms and 5400 rpm. The best SCSI harddrive I know (the Seagate
-Cheetah) runs 7.8ms/10000rpm.
-
-
-
-Fast, big drives are expensive. Really big drives are very
-expensive. Really fast drives are pretty expensive. On the other end,
-really slow, small drives are cheap but not cost effective, because it
-doesn't cost any less to make the cases, ship the drives, and sell
-them.
-
-
-
-In between is a `sweet spot' where moving in either direction
-(cheaper or more expensive) will cost you more than you get out of it. The
-sweet spot moves (towards better value) with time. Right now (July 2001),
-it's about at 18GB drives, 6ms, 10000rpm, ultra2 SCSI. If you can make the
-effort, go to your local computer superstore and write down a dozen or so
-drives they sell `naked'. (If they don't sell at least a dozen hard drives
-naked, find yourself a better store. Use the Web, Luke!) Plot cost against
-size, seek and rotational speed, and it will usually become pretty obvious
-which ones to get for your budget.
-
-
-
-Do look for specials in stores; many superstores buy overstock from
-manufacturers. If this is near the `sweet spot', it's often
-surprisingly cheaper than comparable drives. Just make sure you
-understand the warranty procedures.
-
-
-
-Note that if you need a lot of capacity, you may be better off with
-two (or more) drives than a single, bigger one. Not only can it be cheaper
-but you end up with two separate head assemblies that move independently,
-which can cut down on latency quite a bit (see below).
-
-
-
-Once you've decided which kind of drive(s) you want, you must decide
-how to distribute them over one or more SCSI buses. Yes, you
-''may'' want more than one SCSI bus. (My current desktop
-machine has three.) Essentially, the trick is to make sure that all the
-disks on one bus, talking at the same time, don't exceed the capacity of
-that bus. At this time, I can't recommend anything but an Ultra/Wide SCSI
-controller. This means that the attached SCSI bus can transfer data at up
-to 40MB/s for an Ultra/Wide disk, 20MB/s for an Ultra/narrow disk, and
-10MB/s for a `fast SCSI' disk. These numbers allow you do do your math: an
-8MB/s disk will eat an entire bus on its own if it's `fast' (10MB/s). Three
-6MB/s ultra/narrow disks fit onto one bus (3x6=18MB/s`20MB/s), but just
-barely. Two ultra/wide Cheetahs (12.8MB/s) will share an (ultra/wide) bus
-(25.6`40), but they would collide on an ultra/narrow bus, and any one
-Cheetah would be bandwidth constrained on a (non-ultra) `fast' bus (12.8
-b 10).
-
-
-
-If you find that you need two SCSI buses, you can go with `dual
-channel' versions of many popular SCSI controller cards (including the
-Adaptec). These are simply two controllers on one card (thus taking
-only one PCI slot). This is cheaper and more compact than two cards;
-however, on some motherboards with more than 3 PCI slots, using two
-cards may be somewhat faster (ask me what a PCI bridge is :-).
-
-
-
-How do you deal with slow SCSI devices - CD-ROMS, scanners, tape
-drives, etc.? If you stick these onto a SCSI bus with fast disks,
-they will slow down things a bit. You can either accept that (as in ``I
-hardly ever use my scanner anyway''), or stick them onto a separate
-SCSI bus off a cheap controller card. Or you can (try to) get an ATA
-version to stick onto that inevitable IDE interface on your
-motherboard. The same logic applies to disks you won't normally use,
-such as removables for data exchange.
-
-
-
-If you find yourself at the high end of the bandwidth game, be aware
-that the theoretical maximum of the PCI bus itself is 132MB/s. That
-means that a dual ultra/wide SCSI controller (2x40MB/s) can fill more
-than half of the PCI bus's bandwidth, and it is not advised to add
-another fast controller to that mix. As it is, your device driver
-better be well written, or your entire system will melt down (figuratively
-speaking).
-
-
-
-Incidentally, all of the numbers I used are `optimal' bandwidth
-numbers. The real scoop is usually somewhere between 50-70% of nominal,
-but things tend to cancel out - the drives don't quite transfer as fast
-as they might, but the SCSI bus has overhead too, as does the
-controller card.
-
-
-
-Whether you have a single disk or multiple ones, on one or several
-SCSI buses, you should give careful thought to their partition layout.
-Given a set of disks and controllers, this is the most crucial
-performance decision you'll make.
-
-
-
-A partition is a contiguous group of sectors on the disk. Partitioning
-typically starts at the outside and proceeds inwards. All partitions
-on one disk share a single head assembly. That means that if you try
-to overlap I/O on the first and last partition of a disk, the heads
-must move full stroke back and forth over the disk, which can
-radically increase seek time delays. A partition that is in the
-middle of a partition stack is likely to have best seek performance,
-since at worst the heads only have to move half-way to get there (and
-they're likely to be around the area anyway).
-
-
-
-Whenever possible, split partitions that compete onto different
-disks. For example, /usr and the swap should be on different disks if
-at all possible (unless you have outrageous amounts of RAM).
-
-
-
-Another wrinkle is that most modern disks use `zone sectoring'. The
-upshot is that outside partitions will have higher bandwidth than inner
-ones (there is more data under the heads per revolution). So if you
-need a work area for data streaming (say, a CD-R pre-image to record),
-it should go on an outside (early numbered) partition of a
-fast-rotating disk. Conversely, it's a good convention to put
-rarely-used, performance-uncritical partitions on the inside (last).
-
-
-
-Another notes concerns SCSI mode pages. Each (modern) SCSI disk has a
-small part of its disk (or a dedicated EEPROM) reserved for persistent
-configuration information. These parameters are called `mode pages',
-for the mechanism (in the SCSI protocol) for accessing them. Mode page
-parameters determine, among others, how the disk will write-cache, what
-forms of error recovery it uses, how its RAM cache is organized, etc.
-Very few configuration utilities allow access to mode page parameters
-(I use FWB Toolkit on a Mac - it's simply the best tool I know for that
-task), and the settings are usually factory preset for, uh, Windows 95
-environments with marginal hardware and single-user operation.
-Particularly the cache organization and disconnect/reconnect pages can
-make a tremendous difference in actual performance. Unfortunately
-there's really no easy lunch
here - if you set mode page parameters
-wrong, you can screw up your data in ways you won't notice until months
-later, so this is definitely `no playing with the pushebuttons' territory.
-
-
-
-Ah yes, caches. There are three major points where you could cache I/O
-buffers: the OS, the SCSI controller, and the on-disk controller.
-Intelligent OS caching is by far the biggest win, for many reasons. RAM
-caches on SCSI controller cards are pretty pointless these days; you
-shouldn't pay extra for them, and experiment with disabling them if
-you're into tinkering.
-
-
-
-RAM caches on the drives themselves are a mixed bag. At moderate size
-(1-2MB), they are a potential big win for Windows 95/98, because
-Windows has stupid VM and I/O drivers. If you run a true multi-tasking
-OS like Linux, having unified RAM caches on the disk is a significant
-loss, since the overlapping I/O threads kick each other out of the
-cache, and the disk ends up performing work for nothing.
-
-
-
-Most high-performance disks can be reconfigured (using mode page
-parameters, see above) to have `segmented' caches (sort of like a
-set-associative memory cache). With that configured properly, the RAM
-caches can be a moderate win, not because caching is so great on the
-disk (it's much better in the OS), but because it allows the disk
-controller more flexibility to reschedule its I/O request queue. You
-won't really notice it unless you routinely have b2 I/O requests
-pending at the SCSI level. The conventional wisdom (try it both ways)
-applies.
-
-
-
-And finally I ''do'' have to make a
-disclaimer. Much of the stuff above is shameless simplification. In
-reality, high-performance SCSI disks are very complicated
-beasties. They run little mini-operating systems that are most
-comfortable if they have 10-20 I/O requests pending ''at the
-same time''. Under those circumstances, the amortized global
-latencies are much reduced, though any single request may experience
-''longer'' latencies than if it were the only one
-pending. The only really valid analysis are stochastic-process models,
-which we ''really'' don't want to get into
-here. :-)
-
-----
-!!4.7. Souping Up X Performance
-
-If you care about X performance, be sure you get a graphics card
-with a dedicated blitter and a high-speed local-bus connection. If it
-says "AGP" you have this; AGP is a cross-vendor standard for a local
-bus optimized for graphics.
-
-
-
-These cards speed up X in two ways. First, they offload some
-common screen-painting operations from the main processor onto
-specialized processors on the card itself. Secondly, by using a local
-bus, they make it possible to send commands to the card faster than
-the ISA bus could allow. The combined effect can be eye-poppingly
-fast screen updates even at very high resolutions.
-
-
-
-There's no longer much reason to bother with any of the
-closed-source X servers like !MetroLink or X/Inside. XFree86 now supports
-most of the high-end cards that used to be the special preserve of the
-closed-source X versions.
-
-
-
-If you're feeling really flush, plump for a 17" or even 20"
-monitor. The larger size can make a major difference in viewing comfort.
-Also you'll be set for 1600x1200, which many cards can support these days.
-In the mean time, the bigger screen will allow you to use fonts in smaller
-pixel sizes so that your text windows can be larger, giving you a
-substantial part of the benefit you'd get from higher pixel
-resolutions.
-
-----
-!!!5. Hardware for Backups
-
-You should have a tape drive for backup. Ideally, your tape backup
-should be able to image your entire disk. Choosing a tape drive used to be
-pretty complicated, with a plethora of different formats and media to chose
-from. It's much simpler now that the combination of cheap CD-ROM drives
-and huge hard disks has effectively killed off QIC and other sub-megabyte
-formats. These advances have also killed off a bunch of niche technologies
-for backup, including floptical disks, Bernoulli boxes, Iomega and !SyQuest
-removable drives, and magneto-optical drives -- though the latter have
-survived as casual transfer media -- that is, as a sort of super-capable
-floppy replacement)
-
-
-
-Some people like to burn CDs for backup. While this is a good way to
-archive precious data, the capacity is too low and the media cost too high
-for serious use. Rewritable CD-RWs do make a very nice transfer medium,
-however.
-
-
-
-Digital Data Storage (DDS) capacities are a good match for today's
-multi-gigabyte drives (this is essentially the same technology as
-Digital Audio Tape or DAT). I'm told that Hewlett-Packard DDS devices
-are especially good, not surprising given HP's traditional obsession
-with reliability and overengineering stuff. All the DDSs I know about
-are SCSI devices.
-
-
-
-At the high end, 8mm helical-scan tape (the stuff used in Sony
-camcorders) used to compete with DDS, but DDS drives have now outstripped
-it in capacity and transfer speed. A couple of other tape technologies
-(notably DLT) still do, but their media are extremely expensive.
-
-
-
-Here's a quick summary of the major alternative DDS formats:
-
-
-
-__Table 2. DDS types__
-
-
-!TypeGigabytes (uncompressed)Gigabytes (compressed)Speed (Kbytes/sec)DDS-1 60-meter1.32-4183-366DDS-1 90-meter24-8183-366DDS-2 120-meter57-12183-500DDS-3 120-meter1224700DDS-4 120-meter20401100
-
-DDS tape drives (and tapes) come actually in five variants: DDS,
-DDS-DC, DDS-2, DDS-3, and DDS-4. These are supposed to be downward
-compatible (e.g. DDS-2 reads/writes DDS-DC but not vice versa.) DDS and
-DDS-DC use 60m and 90m tapes; the -DC version adds hardware
-compression. DDS (non-DC) and DDS2 should be considered obsolete.
-
-
-
-The DDS-3 and DDS-4 standards support higher density on the
-tape. DDS-4 is bleeding edge (high premium), but DDS-3 is coming down now,
-and can make the difference between single-tape and and multi-tape backups
-(which can often make the difference between daily backups and "why didn't
-I..." hand-wringing.)
-
-
-
-Don't forget to put the cost of cleaning tapes into your budget. If a
-DDS drive gets dirty heads (determined by the read-after-write error
-rate), it will stop working until the heads are cleaned. DDS drives
-typically start complaining after about 50 full-tape operations.
-
-
-
-SCSI tapes and DDS3 and below normally have the "narrow" 50-pin
-connector. If your controller is "wide" (68 pins) you'll need a cable
-adapter. Better yet is to put a cheap SCSI controller like an AHA 154x in
-the machine just for the tape -- otherwise you might end up plugging a tape
-drive with a single-ended electrical interface into a controller with a
-voltage-differential interface and dragging down the speed of every device
-on the bus.
-
-----
-!!!6. Of Mice And Machines
-
-Mice and trackballs used to be simple; now, thanks to Microsoft,
-they're complicated. Fortunately, XFree86 is now pretty good at
-autodetecting your mouse when it starts up, so if that's what you're
-using you can skip the next section.
-
-----
-!!6.1. Mouse Types
-
-In the beginning, there was only the Mouse
-Systems 3-button serial mouse; this reported status to a serial port
-30 times a second using a 5-byte serial packet encoding now called
-``C'' protocol. The Logitech Series 7 and 9 mice were Mouse
-Systems-compatible. All Unixes that have any mouse support at all
-understand C-protocol serial mice.
-
-
-
-Then Microsoft got into the act. They designed a two-button
-serial mouse which reports only deltas in a three-byte packet; that
-is, it sends changes in button status and motion reports only when the
-mouse is actually moving. This is called `M' protocol. Microsoft
-sold a lot of mice, so Logitech switched from `C' to `M' - but
-they added a third button, state changes for which show up in an
-optional fourth byte. Thus, `M+' protocol, upward-compatible with
-Microsoft's `M'. Most Unix vendors add support for M+ mice, but it's
-wise to check (Linux's XFree86 has it).
-
-
-
-Bus mice are divided into 8255 and !InPort types. These report info
-continuously at 30 or 60 Hz (though !InPort mice have an option for
-reporting deltas only), and you get interrupts on events and then have
-to poll hardware ports for details. Bus mice are no longer widely
-available and there is no good reason to bother with them.
-
-
-
-In addition to serial mice and bus mice, there are ``keyboard
-mice''. On PS/2s there are two identical-looking keyboard ports,
-labeled (with icons) ``mouse'' 8 ``keyboard''. Both are 6-pin
-mini-DINs that look like the regular PC keyboard port only smaller.
-Physically, the connector goes to the keyboard processor (often an
-8042); electrically, it provides TTL levels (serial clock, serial
-data, ground and +5V); logically, it uses the same protocol as normal
-serial mice. The same keyboard processor that decodes the keyboard decodes
-the mouse. PS/2s have this port, many newer motherboards do
-as well. Confusingly, XFree86 thinks these keyboard mice are
-bus mice.
-
-
-
-All things considered, Unix users are probably best off going
-with a serial mouse if their motherboard isn't one of the newer ones
-with a built-in PS/2 mouse. Most current clone motherboards give you
-two serial ports, so you can still dedicate one to this and still have
-one for the all-important modem. Not only are the compatibility
-issues less daunting, but a serial mouse loads the multitasking system
-less due to interrupt frequency.
-
-----
-!!6.2. Buying a Mouse
-
-Beware that most clone vendors, being DOS oriented, bundle
-two-button M-type mice. Thus, you may have to buy your own
-three-button mouse. Ignore the adspeak about dpi and pick a
-mouse or trackball that feels good to your hand.
-
-
-
-Your humble editor really, really likes the Logitech !TrackMarble, an
-optical trackball that eliminates the chronic roller-fouling problems of
-the older !TrackMan. They're well-supported by XFree86 (type !MouseMan), so
-any Linux or BSD will accept them.
-
-----
-!!!7. Modems
-
-This section will give you a thumbnail sketch of the modem types
-available out there, one tuned for the typical Unix installation's
-needs.
-
-----
-!!7.1. The Simple Answer
-
-The modem market has stabilized, with a clear leader at a reasonable
-price. If you can afford it ($270 in August 2001) go buy a U.S. Robotics
-V.Everything external. You can then know that you've got the best and
-skip the rest of this section.
-
-----
-!!7.2. Overview of the Modem Market
-
-The modem market is like consumer electronics (and unlike the
-computer market as a whole) in that price is a very poor predictor of
-performance. For ordinary file transfers, some $50 modems are better than
-some $150 modems. Paying top dollar mainly buys you better tolerance of
-poor connections and better performance at heavy-duty bi-directional
-transfers (such as you would generate, for exmaple, using SLIP or PPP over
-a leased line to an Internet provider).
-
-
-
-In today's market, the typical modem does a nominal 56kbps -- V.90
-plus V.29 or V.17 fax transmission and reception (over plain old phone
-lines you won't get more than 53K of that). You don't see much
-in the way of slow/cheap to fast/expensive product ranges within a
-single brand, because competition is fierce and for many modem board
-designs (those featuring DSP (Digital Signal Processor) chips run by a
-program in ROM) adding a new protocol is basically a software change.
-
-
-
-For much more information on high-speed modems for Unix, see The Linux/Modem
-Compatibility Knowledge Base. The page is aimed at Linux users,
-but the advice is general to any non-Windows OS.
-
-----
-!!7.3. Internal vs. External
-
-Most modems come in two packagings: internal, designed to fit in
-a PC card slot, and external, with its own case, power supply, and
-front-panel lights. Typically you'll pay $20 to $30 more for an
-external modem than you will for the internal equivalent. You'll also
-need a serial port to connect your external modem to.
-
-
-
-Pay that premium - being able to see the blinkenlights on
-the external ones will help you understand and recover from
-pathological situations. For example, if your Unix system is prone to
-``screaming-tty'' syndrome, you'll quickly learn to recognize the
-pattern of flickers that goes with it. Punch the hangup/reset button
-on an external modem and you're done - whereas with an internal
-modem, you have to go root and flounder around killing processes and
-maybe cold-boot the machine just to reset the card.
-
-
-
-See Rick's
-Rants for extended discussion of this point.
-
-----
-!!7.4. Pitfalls to Avoid
-
-If the abbreviation ``RPI'' occurs anywhere on the box, don't even
-consider buying the modem. RPI (Rockwell Protocol Interface) is a
-proprietary ``standard'' that allows modem makers to save a few bucks at
-your expense by using a cheap-jack Rockwell chipset that doesn't do error
-correction. Instead, it hands the job off to a modem driver which (on
-a Unix machine) you will not have.
-
-
-
-Also avoid anything called a ``Windows Modem'' or ``!WinModem'',
-``HCF, or ``HSP''; these lobotomized pieces of crap require a Windows
-DLL to run. They will eat up to 25% of your processor clocks during
-transfers, and hog high-priority interrupts (causing your machine to
-stall under Windows even if your processor still has spare
-cycles).
-
-
-
-Multi-user Unix eats enough processor clocks that you want to be
-sure of good hardware buffering in your UART - that is, enough
-of it to avoid losing characters between modem and PC if the OS is a
-bit slow responding to an interrupt (V.42bis in hardware won't detect
-this!). This means you want a 16550A or equivalent UART. If you're
-using an external modem, this is an issue about your serial-port
-board(s). If you're using an internal modem, the UART is on the modem
-card itself. So, when buying internal modems,
-''ask'' what the UART type is. If the vendor says
-16540, lose them.
-
-
-
-Many fax modems come with bundled MS-DOS fax software that is at
-best useless under Unix, and at worst a software kluge to cover
-inadequate hardware. Avoid these bundles and buy a bare modem -
-it's cheaper, and lowers the likelihood that something vital to your
-communications needs has been left out of the hardware.
-
-
-
-Avoid ``Class 1'' and ``Class 2'' modems. Look for ``Class
-2.'' for the full EIA-standard command set.
-
-----
-!!7.5. What to Buy
-
-What you want, these days, is a V.90 modem. V.90, formally,
-is the ITU-T recommendation for asymmetric data signalling
-rates of up to 56Kbps in the direction of a digitally connected server
-to a capable client, and up to 33.6Kbps in the direction of the client
-to the server.
-
-
-
-The technology is based on eliminating restrictions imposed by the
-conversion of analog signals to digital form in the downstream data path
-(server -b client). Data flow in the server to client direction does not
-occur in the form of a modulated carrier, it is instead sent as binary
-numbers representative of 256 possible voltage levels. The reason for the
-asymmetrical send/receive rates is because in the direction from the client
-to the server it is not possible to use a digital coding scheme and make it
-work as well as V.34 does, thus V.34 is used instead. It isn't possible
-because the telco's line card has a codec that is a much better digital
-level changer for the transmit direction than it is for the receive
-direction. The codec used in the customer's modem is, in that respect,
-somewhat more sophisticated and was designed to work as a fairly good level
-changer in the receive direction (which the telco's codec was not designed
-to do).
-
-
-
-Note: Achievable bit rates are limited to less than 56kbps in
-the United States by FCC regulations that limit power input to the
-network.
-
-
-
-Beyond the V series, the telcos are pushing a technology called ADSL
-(Asymmetric Digital Subscriber Line). This method converts existing
-twisted-pair telephone lines into access paths for multimedia and high
-speed data communications. ADSL transmits more than 6Mbps to a
-subscriber, and as much as 640 kbps more in both directions.
-
-
-
-An ADSL circuit connects an ADSL modem on each end of a
-twisted-pair phone line, creating three information channels; a high
-speed downstream channel, a medium speed duplex channel, and a POTS
-(Plain Old Telephone Service) channel. The POTS channel is split off
-from the digital modem by filters, thus guaranteeing uninterrupted
-POTS, even if ADSL fails. The high speed channel ranges from 1.5 to
-6.1 Mbps, while duplex rates range from 16 to 640 kbps. Each channel
-can be sub-multiplexed to form multiple, lower rate channels.
-
-----
-!!7.6. Fax Modems
-
-Fax capability is included with most all modems these days; it's
-cheap for manufacturers, being basically a pure software add-on. The
-CCITT also sets fax protocol standards. Terms to know:
-
-
-
-
-
-; V.29:
-
- CCITT standard for Group III fax encoding at 9600bps
-
-; V.17:
-
- CCITT standard for Group III fax encoding at
-14400bps
-
-
-
-V.17 isn't common yet, but it doesn't usually cost extra over
-V.29 when you find it.
-
-
-
-There's a separate series of standards for software control of fax
-modems over the serial line maintained by the Electronics Industry
-Association and friends. These are:
-
-
-
-''Class 1'' - base EIA standard for fax
-control as extensions to the Hayes AT command set.
-
-
-
-''Class 2.'' - enhanced EIA standard
-including compression, error correction, station ID and other
-features.
-
-
-
-''Class 2'' - marketroidian for
-anything between Class 1 and Class 2.. Different ``Class 2'' modems
-implement different draft subsets of the 2.0 standard, so ``Class 2''
-fax software won't necessarily drive any given ``Class 2''
-modem.
-
-
-
-There's also a proprietary Intel "standard" called CAS, Communicating
-Applications Specification. Ignore it; only Intel products support it.
-
-
-
-The GNU toolset includes a freeware fax transmission and reception
-toolset, Netfax. Look for it at prep.ai.mit.edu:pub/gnu/fax-*. It
-says it requires a modem conforming to the ``Class 2'' control
-standard, but you'd be safest getting a 2.-conformant modem for
-reasons explained above. Netfax also requires GNU Ghostscript to do
-Postscript handling for it.
-
-----
-!!!8. CD-ROMs and Multimedia Hardware
-!!8.1. CD-ROM Drives
-
-Standard CD-ROMs hold about 650 megabytes of read-only data in a
-format called ISO-9660 (formerly ``High Sierra''). All current Unixes
-now support these devices. In fact, most Unix and Linux software is
-now distributed on ISO-9660 CD-ROM, a cheaper and better method than
-the QIC tapes we used to use.
-
-
-
-CD-ROM drives may be driven through SCSI, through enhanced IDE
-(ATAPI), or through a proprietary interface card (like the Mitsumi and
-Sony interfaces). Unix support for CD-ROMs is usually through SCSI
-drivers (exception: BSDI/386 supports the Mitsumi interface; Linux
-supports the Mitsumi and Sony interfaces). I recommend that you avoid
-the proprietary cards; they will effectively cost you money when you
-need to upgrade. Besides, street prices for SCSI CD-ROMS have
-dropped below $200.
-
-
-
-(A few external CD-ROMs come with a parallel-port interface.
-Avoid these; they tend to have very slow transfer rates.)
-
-
-
-Any CD-ROM you buy should be at least a ``double-spin'' drive
-meeting the MPC2 (Multimedia PC) standard of a 300K/sec transfer rate
-when reading. digital data. The older single-speed drives, which only
-supported the 150K/sec rate Red Book standard for audio CDs, are
-obsolete. The lowest speed you can buy these days is 4X (600K/sec).
-6X, 8X, 10X, 12X, 24X, 32X, 40X, and 56X are available.
-
-
-
-The next level up in CD hardware standards is CD-ROM XA. So
-far, drives that support XA are few and expensive. It's not yet in
-wide use in the DOS/Windows world, and I don't know of any Unix
-support for it, either in closed- or open-source code.
-
-
-
-CD-ROM access times about 280ms for high-end double-speed drives (to
-put this in perspective, it's about 30 times slower than a typical 9ms hard
-disk, but considerably faster than a tape). Accordingly, modern 32X
-drives are about half the speed of a hard drive.
-
-
-
-Most CD-ROMS will include a headphone jack so you can play audio
-CDs on them. Better-quality ones will also include two RCA jacks for
-use with speakers. Another feature to look for is a drive door or
-seal that protects the drive head from dust.
-
-
-
-CD-ROM formats are still an area of some confusion. A slight
-enhancement of the original ``High Sierra'' CD-ROM filesystem format
-(designed for use with DOS, and limited to DOS's 8+3 file-naming
-convention) has been standardized as ISO-9660.
-
-
-
-There is a de-facto Unix standard called `Rock Ridge' pioneered by the
-Sun User's Group shareware CD-ROMs. This is a way of putting an extra
-layer of indirection on an ISO-9660 layout that preserves Unix's long
-dual-case filenames. Some Unixes (notably Linux, netBSD, freeBSD and
-BSD/OS) can mount Rock Ridge filesystems.
-
-
-
-More much more detail on CD-ROMs, CD-ROM standards and how to
-buy drives is available in the alt.cdrom FAQ, available for FTP as cdrom.com:/cdrom/faq. It is also
-archived in the news.answers tree at rtfm. This FAQ includes
-comparison tables tables of numerous drive types, CD-ROM sources, and
-ordering information.
-
-----
-!!8.2. Sound Cards and Speakers
-
-Look for the following features as a minimum in your sound card:
-
-
-
-
-
-
-****
-
-16-bit sampling (for 65536 dynamic levels rather
-than 256).
-
-
-****
-****
-
-Mono and stereo support.
-
-
-****
-****
-
-Full-duplex mode.
-
-
-****
-****
-
-Sampling rates ranging fron 8K/sec (voice-quality)
-through 11KHz (AM-radio quality), 22KHz (FM-radio quality) and
-standard audio (44.1KHz).
-
-
-****
-****
-
-MIDI interface via a standard 15-pin D-shell
-connector.
-
-
-****
-****
-
-RCA output jacks for headphones or speakers.
-
-
-****
-****
-
-A microphone jack for sound input.
-
-
-****
-
-The most important feature is your sound card is what type of MIDI
-synthesis it has. All current sound cards have some sort of MIDI (musical
-instrument digital interface) compliance, but if nothing else, make
-sure your card supports the General MIDI standard. MIDI is just a set
-of commands issued by the application that tells the sound card which
-instrument to play, at what note, and for what duration.
-
-
-
-Older and cheaper cards use FM synthesis. This synthesis uses a
-combination of sine waves to imitate the sounds of the different
-instruments. The result is like the sound tracks of most computer
-games sold a few years ago; imitation music with an arcade-like
-sound.
-
-
-
-The method used by most modern sound boards is called wave table
-synthesis. In this method, digitized samples of actual instrument
-sounds are used as templates for the tones generated by the MIDI
-commands. Wave table cards vary in the quantity and quality of
-samples; one figure of merit often quoted is the wave table ROM size
-(often 4MB or 8MB). Also some boards have wavetable RAM that can
-store samples loaded from a disk.
-
-
-
-Soundcards with DSP (Digital Signal Processing) can perform synthesis
-effects on board, relieving the CPU for other tasks. Some DSP chips
-are even software-programmable. Some high-end cards even include 3D
-sound effects. Whether the system used is SRS (Sound Retrieval
-System), Q-Sound, or Spatializer, it is designed to improve the
-perceived stereo effect of your speakers. These 3D effects work by
-delaying the timing of certain portions of the audio signal so that
-different frequencies hit your ear at slightly different times. The
-downside is that some of the cards equipped with 3D sound add a
-noticeable amount of noise to the card's output.
-
-
-
-If you play a lot of computer games, you'll need to pay attention to
-compatibility. DOS games are written almost exclusively for the
-Creative Labs specification; you will need a card that is 100% Sound
-Blaster compatible. Many vendors do not license the Creative Labs
-specification but claim that their cards are 100% game
-compatible. This means that the sound will work, but not all sounds
-that you hear will be the ones that the game programmers intended. If
-you play many DOS games, it would be best to buy a Sound Blaster and
-save yourself a migraine.
-
-
-
-Lastly, try to avoid sound cards with built-in amplifiers that are
-more powerful than 4 watts/channel. Sound cards that have more
-powerful amplifiers are said to have the problem of adding noise to the
-card's output. Use powered speakers with a 4 watt/channel card to
-solve this problem. Most cards are equipped with 4 watts/channel
-anyway. Wavetable cards are so inexpensive these days that it's almost
-worth their additional cost over a regular FM synthesis card. If you
-decide to settle for an FM card, make sure that there is a
-daughterboard made for the card that will let you upgrade to wavetable
-synthesis. In some cases, however, the wavetable card is cheaper than
-buying an FM card and then deciding that you want the wavetable
-upgrade. If you do decide on the wavetable as your card of choice, PC
-Magazine rated the best MIDI wavetables (MIDI being the most important
-feature in my opinion) the Media Vision Premium 3-D, Media Vision Pro
-3-D, Creative Labs Sound Blaster AWE32, and the Turtle Beach Monterey
-(although there are value editions of the Sound Blaster 32 that have
-fewer ROM instrument samples but maintain the superior MIDI wavetable
-synthesis).
-
-
-
-Linux, includes drivers for the !SoundBlaster series and many
-other boards including the PAS Adlib, the Gravis Ultrasound, and the
-!ProAudioSpectrum. Many of these are included in the 2.0 and newer
-kernels. See the OSS/Free home
-page for details
-
-
-
-Warning: some sound cards require a specific CD-ROM type! Avoid
-these.
-
-
-
-In speakers, look for a magnetically-shielded enclosure with volume,
-bass and treble controls. Some speakers run off the card's 4-watt
-signal; others are ``self-powered'', using batteries or a separate
-power supply. Your major buying choice is which one of these options
-to pursue.
-
-
-
-Generally speaking, you'll get better value if you buy your
-sound card, CD-ROM, and speakers not separately but as a bundled
-``multimedia upgrade kit'' (even though Unix users will usually have
-to throw out the bundled software).
-
-
-
-One final, important tip: that audio cable from your CD-ROM back
-to the sound card is used only when you play audio CD-ROMs through
-your speakers. Software-generated sound goes through the system bus,
-so you can play ``Doom'' with sound even if your sound board won't
-accept the audio cable connector.
-
-----
-!!!9. Special considerations when buying laptops
-
-Up until about 1999 the laptop market was completely crazy. The
-technology was in a state of violent flux, with ``standards'' phasing
-in and out and prices dropping like rocks. Things are beginning to
-settle out a bit more now.
-
-
-
-One sign of this change is that there are now a couple of laptop lines
-that are clear best-of-breeds for reasons having as much to do with
-good industrial design and ergonomics as the technical details of the
-processor and display.
-
-
-
-In lightweight machines, I'm a big fan of the Sony VAIO line.
-I owned one from early 1999 until it physically disintegrated under
-the rigors of travel in late 2000, and could hardly imagine
-switching. They weigh 3.5 pounds, give you an honest 3 hours of life
-per detachable battery pack, have a very nice 1024x768 display, and
-are just plain ''pretty''. Their only serious
-drawback is that they're not rugged, and often fall apart after
-a year or so of use.
-
-
-
-If you want a full-power laptop that can compete with or replace
-your desktop machine, the IBM !ThinkPad line is the bomb. Capable,
-rugged, and nicely designed (though somewhat heavyweight for my
-taste). I now use a !ThinkPad X20, the lightest and smallest machine
-in the line, and like it a lot.
-
-
-
-These machines are not cheap, though. If you're trying to save
-money by buying a no-name laptop, here are things to look for:
-
-
-
-First: despite what you may believe, the most important aspect
-of any laptop is ''not'' the CPU, or the disk, or the
-memory, or the screen, or the battery capacity. It's the keyboard
-feel, since unlike in a PC, you cannot throw the keyboard away and
-replace it with another one unless you replace the whole computer.
-''Never buy any laptop that you have not typed on for a couple
-hours''. Trying a keyboard for a few minutes is not enough.
-Keyboards have very subtle properties that can still affect whether
-they mess up your wrists.
-
-
-
-A standard desktop keyboard has keycaps 19mm across with 7.55mm
-between them. If you plot frequency of typing errors against keycap
-size, it turns out there's a sharp knee in the curve at 17.8
-millimeters. Beware of ``kneetop'' and ``palmtop'' machines, which
-squeeze the keycaps a lot tighter and typically don't have enough
-oomph for Unix anyway; you're best off with the "notebook" class
-machines that have full-sized keys.
-
-
-
-Second: be careful that your laptop meets the minimum core and disk
-requirements for the Unix you want to run. This is generally not a problem
-with desktop machines, which can be upgraded cheaply and easily, but laptops
-often have more stringent constraints.
-
-
-
-Third: with present flatscreens, 1024x768 color is the best you're
-going to do (though that may change soon). If you want more than that
-(for X, for example) you have to either fall back to a desktop or make
-sure there's an external-monitor port on the laptop (and many laptops
-won't support higher resolution than the flatscreen's).
-
-
-
-Fourth: look for Nickel-Metal-Hydride (NiMH) batteries, as
-opposed to the older (Nickel-Cadmium) !NiCad type. NiMH batteries are
-great because they have considerably higher energy capacity per pound
-that !NiCads. They need special circuitry to charge them fast, so
-don't try to throw out your !NiCads and replace them with NiMH cells if
-you use a fast charger intended for !NiCads. Both kinds of cells can
-be damaged by overcharging at rates faster than 10 hours per full
-charge.
-
-
-
-Fifth: Older laptop electronics were 5-volt CMOS. Most current
-designs are 3.3-volt CMOS with power-management features on the processor
-(these are often labelled APM, Advanced Power Management). Buy this, if
-you can, to nearly double your use time between recharges.
-
-
-
-Sixth: about those vendor-supplied time-between-recharge
-figures; ''don't believe them''. They collect those
-from a totally quiescent machine, sometimes with the screen or hard
-disk turned off. Under DOS, you'd be lucky to get half the endurance
-they quote; under Unix, which hits the disk more often, it may be less
-yet. Figures from magazine reviews are more reliable.
-
-
-
-Seventh: You probably want a color dual-scan display. It used
-to be that you had to choose between passive-matrix LCD (cheap,
-miserable color) and active- matrix LCD (great color, horribly
-expensive). Dual-scan passive-matrix is nearly as good as
-active-matrix, except for the narrower viewing angle, and it's much
-cheaper. Avoid the older single-scan models, sometimes marketed as
-having STN (super-twisted nematic) displays.
-
-
-
-Eighth: get either a CD-ROM drive or an Ethernet card.
-Otherwise initial load of your Unix could turn into a serious
-problem...
-
-----
-!!!10. How to Buy
-!!10.1. When to Buy
-
-It used to be that good configurations for Unix were what the market
-called `server' machines, with beefed-up I/O subsystems and fast
-buses. No longer; today's `servers' are monster boxes with multiple
-power supplies and processors, gigabytes of memory, and
-industrial-grade air cooling -- they're not really suitable as
-personal machines. A typical SCSI desktop workstation is as much as
-you'll need.
-
-
-
-Prices keep dropping, so there's a temptation to wait forever to
-buy. A good way to cope with this is to configure your system on paper, get
-a couple of initial estimates, then set a trigger price, below the
-lowest one, at what you're willing to pay. Then watch and wait. When
-the configuration cost hits your trigger price, place your order.
-
-
-
-The advantage of this method is that it requires you to settle in your
-mind, well in advance, what you're willing to pay for what you're
-getting. That way, you'll buy at the earliest time you should, and
-won't stress too much out afterwards as it depreciates.
-
-
-
-Before you shop, do your homework. Publications like "Computer
-Shopper" (and their web site at http://www.computershopper.com) are invaluable for helping you
-get a feel for prices and what clonemakers are doing. Another
-excellent site is ComputerESP.
-
-----
-!!10.2. Where to Buy
-
-The most important where-to-buy advice is negative. Do
-''not'' go to a traditional, business-oriented
-storefront dealership. Their overheads are high. So are their
-prices.
-
-
-
-Especially, run -- do not walk -- away from any outfit that trumpets
-`business solutions'. This is marketing code for the kind of place that
-will justify a heavy price premium by promising after-sale service and
-training which, nine times out of ten, will turn out to be nonexistent or
-incompetent. Sure, they'll give you plush carpeting and a firm handshake
-from a guy with too many teeth and an expensive watch -- but did you really
-want to pay for that?
-
-
-
-There are two major alternatives to storefront dealerships and one
-minor one. The major ones are mail order and computer superstores.
-The minor one is computer fairs.
-
-----
-!!10.3. Computer Fairs
-
-I used to be a big fan of hole-in-the-wall stores run by immigrants
-from the other side of the International Date Line, but most of those
-places have been driven out of the regular retail game by the
-superstores. The only place you find diaspora Chinese and Indians
-selling cheap PCs over the counter anymore is at computer fairs.
-(Usually they're doing it to publicize a mail-order business.)
-
-
-
-You can find good `loss-leader' deals on individual parts at these
-fairs (they're especially good places to buy disk drives cheap). But I
-call them a minor alternative because it's hard to get a custom
-SCSI-based configuration tuned for Unix built for you at a fair. So
-you end up, effectively, back in the mail-order or Web channel.
-
-----
-!!10.4. Mail Order
-
-Direct-mail or Web buying makes a lot of sense today for anyone with
-more technical savvy than J. Random Luser in a suit. Even from
-no-name mail-order houses, parts and system quality tend to be high
-and consistent, so conventional dealerships don't really have much
-more to offer than a warm fuzzy feeling. Furthermore, competition has
-become so intense that even mail-order vendors today have to offer not
-just lower prices than ever before but warranty and support policies
-of a depth that would have seemed incredible a few years back. For
-example, many bundle a year of on-site hardware support with their
-medium- and high-end "business" configurations for a very low premium
-over the bare hardware.
-
-
-
-Note, however, that assembling a system yourself out of
-mail-order parts is ''not'' likely to save you money
-over dealing with the mail-order systems houses. You can't buy parts
-at the volume they do; the discounts they command are bigger than the
-premiums reflected in their prices. The lack of any system warranty
-or support can also be a problem even if you're expert enough to do
-the integration yourself - because you also assume all the risk
-of defective parts and integration problems.
-
-
-
-Cruise through `Computer Shopper' and similar monthly ad compendia.
-Even if you decide to go with a conventional dealer, this will tell you
-what ''their'' premiums look like. These days most
-mail-order outfits with enough cash to advertise on glossy paper are good
-risks.
-
-
-
-Watch out for dealers (Spectrum Trading for one) who charge ridiculous
-shipping fees. One of our spies reports he bought a hotswappable hard
-disc drive tray that weighed about 3 lbs. and cost $250 and they
-charged $25 to ship it UPS groud.
-
-
-
-Don't forget that (most places) you can avoid sales tax by buying from an
-out-of-state mail-order outfit, and save yourself 6-8% depending on where you
-live. If you live near a state line, buying from a local outfit you can often
-win, quite legally, by having the stuff shipped to a friend or relative just
-over it. Best of all is a buddy with a state-registered dealer number; these
-aren't very hard to get and confer not just exemption from sales tax but
-(often) whopping discounts from the vendors. Hand him a dollar afterwards to
-make it legal.
-
-
-
-(Note: I have been advised that you shouldn't try the latter tactic in
-Florida -- they are notoriously tough on "resale license" holders).
-
-
-
-(Note II: The Supreme Court has ruled that states may not tax
-out-of-state businesses under existing law, but left the way open for
-Congress to pass enabling legislation. Let's hope the mail-order
-industry has good lobbyists.)
-
-----
-!!10.5. Computer Superstores
-
-Big chain superstores like CompUSA and Circuit City give you a
-reasonable alternative to mail order. And there are good reasons to
-explore it -- these stores buy and sell at volumes that allow them to
-offer prices not far above mail-order. (They make back a lot of
-their margin on computer games and small accessories like mouse pads,
-cables, and floppy disks.)
-
-
-
-One thing you should not buy mail-order if you can avoid it is a
-monitor. Monitors are subject to substantial quality variations even
-within the same make and model. Also, one good bump during shipping
-can twist the yoke on a monitor so the image is tilted with respect to
-the bezel. So buy your monitor face-to-face, picking the best out of
-three or four.
-
-
-
-Another good argument for buying at a superstore is that you may
-have to pay return postage if you ship a mail-order system back. On a
-big, heavy system, this can eat your initial price savings.
-
-
-
-The only major problem with superstores is that the salespeople who
-staff them aren't very bright or very clueful (it's a sort of Darwinian
-reverse-selection effect; these are the guys who are fascinated by computer
-technology but not smart enough to be techies). Most of them don't know
-from Linux and are likely to push things like two-button mice and (worse!)
-controllerless modems, that you can't use. Use caution and check your
-system manifest.
-
-
-
-But if you shop carefully and don't fall for one of their
-name-brand "prestige" systems, you can get prices comparable to mail
-order with the comfort of knowing there's a trouble desk you can drive
-back to in a pinch. (Also, you ''can'' see your
-monitor before you buy!)
-
-----
-!!10.6. Other Buying Tips
-
-You can often get out of paying tax just by paying cash,
-especially at computer shows. You can always say you're going to ship
-the equipment out of the state.
-
-
-
-A lot of vendors bundle DOS or Windows and variable amounts of apps
-with their hardware. If you tell them to lose all this useless cruft
-they may shave $50 or $100 off the system price.
-
-----
-!!!11. Questions You Should Always Ask Your Vendor
-!!11.1. Minimum Warranty Provisions
-
-The weakest guarantee you should settle for in the mail-order
-market should include:
-
-
-
-
-
-
-****
-
-72-hour burn-in to avoid that sudden infant death
-syndrome. (Also, try to find out if they do a power-cycling test and
-how many repeats they do; this stresses the hardware much more than
-steady burn-in.)
-
-
-****
-****
-
-30 day money-back guarantee. Watch out for fine print
-that weakens this with a restocking fee or limits it with
-exclusions.
-
-
-****
-****
-
-1 year parts and labor guarantee (some vendors give 2
-years).
-
-
-****
-****
-
-1 year of 800 number tech support (many vendors give
-lifetime support).
-
-
-****
-
-Additionally, many vendors offer a year of on-site service free.
-You should find out who they contract the service to. Also be sure
-the free service coverage area includes your site; some unscrupulous
-vendors weasel their way out with "some locations pay extra", which
-translates roughly to "through the nose if you're further away than
-our parking lot".
-
-
-
-If you're buying store-front, find out what they'll guarantee beyond the
-above. If the answer is "nothing", go somewhere else.
-
-----
-!!11.2. Documentation
-
-Ask your potential suppliers what kind and volume of documentation
-they supply with your hardware. You should get, at minimum,
-operations manuals for the motherboard and each card or peripheral;
-also an IRQ list. Skimpiness in this area is a valuable clue that
-they may be using no-name parts from Upper Baluchistan, which is not
-necessarily a red flag in itself but should prompt you to ask more
-questions.
-
-----
-!!11.3. A System Quality Checklist
-
-There are various cost-cutting tactics a vendor can use which
-bring down the system's overall quality. Here are some good questions
-to ask:
-
-
-
-
-
-
-****
-
-If you're buying a factory-configured system, does it
-have FCC certification? While it's not necessarily the case that a
-non-certified system is going to spew a lot of radio-frequency
-interference, certification is legally required - and becoming
-more important as clock frequencies climb. Lack of that sticker may
-indicate a fly-by-night vendor, or at least one in danger of being
-raided and shut down! (For further discussion, see the section on Radio Frequency Interference
-above.)
-
-
-****
-****
-
-Are the internal cable connectors keyed, so they can't
-be put in upside down? This doesn't matter if you'll never, ever
-''ever'' need to upgrade or service your system.
-Otherwise, it's pretty important; and, vendors who fluff this detail
-may be quietly cutting other corners.
-
-
-****----
-!!!12. Things to Check when Buying Mail-Order
-!!12.1. Tricks and Traps in Mail-Order Warranties
-
-Reading mail-order warranties is an art in itself. A few tips:
-
-
-
-Beware the deadly modifier ``manufacturer's'' on a warranty;
-this means you have to go back to the equipment's original
-manufacturer in case of problems and can't get satisfaction from the
-mail-order house. Also, manufacturer's warranties run from the date
-''they'' ship; by the time the mail-order house
-assembles and ships your system, it may have run out!
-
-
-
-Watch for the equally deadly ``We do not guarantee
-compatibility''. This gotcha on a component vendor's ad means you may
-not be able to return, say, a video card that fails to work with your
-motherboard.
-
-
-
-Another dangerous phrase is ``We reserve the right to substitute
-equivalent items''. This means that instead of getting the
-high-quality name-brand parts advertised in the configuration you just
-ordered, you may get those no-name parts from Upper Baluchistan
-- theoretically equivalent according to the spec sheets, but
-perhaps more likely to die the day after the warranty expires.
-Substitution can be interpreted as ``bait and switch'', so most
-vendors are scared of getting called on this. Very few will hold
-their position if you press the matter.
-
-
-
-Another red flag: ``Only warranted in supported environments''.
-This may mean they won't honor a warranty on a non-DOS system at all,
-or it may mean they'll insist on installing the Unix on disk
-themselves.
-
-
-
-One absolute show-stopper is the phrase ``All sales are final''.
-This means you have ''no'' options if a part doesn't
-work. Avoid any company with this policy.
-
-----
-!!12.2. Special Questions to Ask Mail-Order Vendors Before Buying
-
-
-
-
-****
-
-Does the vendor have the part or system presently in
-stock? Mail order companies tend to run with very lean inventories;
-if they don't have your item in stock, delivery may take longer.
-Possibly ''much'' longer.
-
-
-****
-****
-
-Does the vendor pay for shipping? What's the delivery
-wait?
-
-
-****
-****
-
-If you need to return your system, is there a
-restocking fee? and will the vendor cover the return freight? Knowing
-the restocking fee can be particularly important, as they make keep
-you from getting real satisfaction on a bad major part. Avoid dealing
-with anyone who quotes more than a 15% restocking fee - and it's
-a good idea, if possible, to avoid any dealer who charges a restocking
-fee at all.
-
-
-****
-
-Warranties are tricky. There are companies whose warranties are
-invalidated by opening the case. Some of those companies sell
-upgradeable systems, but only authorized service centers can do
-upgrades without invalidating the warranty. Sometimes a system is
-purchased with the warranty already invalidated. There are vendors
-who buy minimal systems and upgrade them with cheap RAM and/or disk
-drives. If the vendor is not an authorized service center, the
-manufacturer's warranty is invalidated. The only recourse in case of
-a problem is the vendor's warranty. So beware!
-
-----
-!!12.3. Payment Method
-
-It's a good idea to pay with !AmEx or Visa or !MasterCard; that
-way you can stop payment if you get a lemon, and may benefit from a
-buyer-protection plan using the credit card company's clout (not all
-cards offer buyer-protection plans, and some that do have restrictions
-which may be applicable). However, watch for phrases like ``Credit
-card surcharges apply'' or ``All prices reflect 3% cash discount''
-which mean you're going to get socked extra if you pay by card.
-
-
-
-Note that many credit-card companies have clauses in their
-standard contracts forbidding such surcharges. You can (and should)
-report such practices to your credit-card issuer. If you already paid
-the surcharge, they will usually see to it that it is returned to you.
-Credit-card companies will often stop dealing with businesses that
-repeat such behavior.
-
-----
-!!12.4. Which Clone Vendors to Talk To
-!12.4.1. Some pans
-
-''Dell'': treated the Unix community, customers
-and its own employees very badly back in 1994 by making an internal
-decision to kill its market-leading SVr4 port, then obfuscating and
-lying about its intentions for months after its actions made the
-direction clear. On the other hand, they started getting serious
-about Linux in early 2000. I won't say boycott them the way I used
-to, but I will say you ought to think other vendors instead.
-
-
-
-''Gateway'': may also be a vendor to avoid.
-Apparently their newer machines don't have parity bits in their
-memories; memory is tested only on reboot. This is dubious design
-even for DOS, and totally unacceptable for Unix.
-
-----
-!12.4.2. Some picks
-
-The hardware business that VA Linux Systems used to run is, alas, no
-more. ''Requiesciat in pace.'' They made damn good stuff
-(and yes, I thought so long before they made me a director of the
-corporation).
-
-
-
-In early August 2001 I designed an `Ultimate Linux Box' with Gary
-Sandine and John Pearson of Los Alamos
-Computers; it will be described in a forthcoming ''Linux
-Journal'' article. These guys know what they are doing and are
-fun to work with. If you need a high-end Linux workstation, or your
-laboratory needs a computer cluster, talk with them.
-
-----
-!!!13. After You Take Delivery
-
-Your configuration is custom and involves slightly unusual
-hardware. Therefore, keep a copy of the configuration you wrote down,
-and check it against the invoice and the actual delivered hardware.
-If there is a problem, calling back your vendor right away will
-maximize your chances of getting the matter settled quickly.
-
-----
-!!!14. Software to go with your hardware
-
-I used to maintain an entire separate FAQ on Unixes for 386/486 and
-Pentium hardware. Times change, industries evolve, and I can now
-replace that FAQ with just three words:
-
-
-
-__Go get Linux!__
-
-----
-!!!15. Other Resources on Building Linux PCs
-
-Andrew Comech's
-The Cheap /Linux/ Box page is a useful guide to building with
-current hardware that is updated every two weeks. Andrew also
-maintains a short-cut version.
-
-
-
-The Caveat
-Emptor guide has an especially good section on evaluating
-monitor specifications.
-
-
-
-Dick Perron has a PC Hardware
-Links page. There is lots and lots of good technical stuff
-linked to here. Power On Self Test codes, manufacturer address lists,
-common fixes, hard disk interface primer, etc.
-
-
-
-Anthony Olszewski's Assembling A
-PC is an excellent guide to the perplexed. Not
-Linux-specific. If you're specifically changing a motherboard, see
-the
-Installing a Motherboard page. This one even has a Linux note.
-
-
-
-Tom's Hardware
-Guide covers many hardware issues exhaustively. It is
-especially good about CPU chips and motherboards. Full of ads and
-slow-loading graphics, though.
-
-
-
-The System Optimization
-Site has many links to other worthwhile sites for hardware
-buyers.
-
-
-
-Christopher B. Browne has a page on Linux VARs
-that build systems. He also recommends the Linux
-VAR HOWTO.
-
-
-
-Jeff Moe has a Build
-Your Own PC page. It's more oriented towards building from
-parts than this one. Less technical depth in most areas, but better
-coverage of some including RAM, soundcards and motherboard
-installation. Features nifty and helpful graphics, one of the better
-graphics-intensive pages I've seen. However, the hardware-selection
-advice is out of date.
-
-
-
-The Linux Hardware
-Database provides, among other things (e.g., drivers, specs, links,
-etc.), user ratings for specific hardware components for use under
-Linux. Our ratings take a lot of the guess work out of choosing which
-hardware to buy for a Linux box. The site also provides several
-product-specific resources (i.e., drivers, workarounds, how-to) that
-help users get hardware working after they have made a purchase.
-
-----
-!!!16. Upgrading Older Machines
-!!16.1. Older Memory Types
-
-The last-generation memory package was a SIMM (Single In-Line
-Memory Module). We include some information on these here for people
-upgrading old systems.
-
-
-
-SIMMs have 9 bits wide (8 bits of data, one for parity) and
-either 1, 4, or 16 megabytes in size. The 16s are slightly cheaper per
-megabyte.
-
-
-
-There are two physical SIMM sizes; 30-pin and 72-pin. The 30-pin size
-is long obsolete; most SIMM-using motherboards have exclusively 72-pin
-sockets.
-
-
-
-Also, your memory may or may not have on-board parity check bits.
-Memory with parity is specified as ``x36'' (4 check bits per word);
-memory without is ``x32''. Some motherboards require parity memory;
-some (including those based on the Neptune chipset) can use parity if
-present; some (including those based on the Triton chipset) cannot use
-it. Parity memory is a good idea for Unix machines, which stress the
-hardware more than other OSs.
-
-
-
-You'll hear a lot about ``EDO'' (Extended Data Out) RAM. This stuff is
-5%-10% more expensive, but that pays for a significant performance
-boost in ``burst mode'' (that is, when fetching large contiguous
-sections of memory into the cache). Most current motherboards
-(including those based on the Triton chipset) can use
-EDO but don't require it.
-
-
-
-You do ''not'' want to buy 1MB SIMMs any more,
-unless you're filling out memory in an existing system configured with
-1MB SIMMs. The trouble with these (besides the fact that four of them
-are more expensive than a 4MB chip) is that, due to interleaving
-constraints, you'll probably have to throw them away if you ever add
-more memory.
-
-
-
-These interleaving constraints differ from motherboard to
-motherboard. Typically, memory sockets are set up in banks of either
-2 or 4, with a requirement that you fill all sockets of each bank with
-the same size of chip. Also, if you mix chip sizes in the banks, the
-sizes have to decrease smoothly (so there won't be gaps in the memory
-address space).
-
-
-
-So your possible configurations look like the following table.
-All of these are possible on 4-bank, 16-slot boards; only the
-asterisked ones are possible on 2-bank, 8-slot boards. All the
-capacities above 64MB require that the board accept 16MB SIMMs. All
-current 2x8 boards accept these.
-
-
- * 4MB = 1-1-1-1
-* 8MB = 1-1-1-1 + 1-1-1-1
-12MB = 1-1-1-1 + 1-1-1-1 + 1-1-1-1
-16MB = 1-1-1-1 + 1-1-1-1 + 1-1-1-1 + 1-1-1-1
-* 16MB = 4-4-4-4
-* 20MB = 4-4-4-4 + 1-1-1-1
-24MB = 4-4-4-4 + 1-1-1-1 + 1-1-1-1
-28MB = 4-4-4-4 + 1-1-1-1 + 1-1-1-1 + 1-1-1-1
-* 32MB = 4-4-4-4 + 4-4-4-4
-36MB = 4-4-4-4 + 4-4-4-4 + 1-1-1-1
-40MB = 4-4-4-4 + 4-4-4-4 + 1-1-1-1 + 1-1-1-1
-48MB = 4-4-4-4 + 4-4-4-4 + 4-4-4-4
-52MB = 4-4-4-4 + 4-4-4-4 + 4-4-4-4 + 1-1-1-1
-64MB = 4-4-4-4 + 4-4-4-4 + 4-4-4-4 + 4-4-4-4
-* 64MB = 16-16-16-16
-* 68MB = 16-16-16-16 + 1-1-1-1
-72MB = 16-16-16-16 + 1-1-1-1 + 1-1-1-1
-76MB = 16-16-16-16 + 1-1-1-1 + 1-1-1-1 + 1-1-1-1
-* 80MB = 16-16-16-16 + 4-4-4-4
-84MB = 16-16-16-16 + 4-4-4-4 + 1-1-1-1
-88MB = 16-16-16-16 + 4-4-4-4 + 1-1-1-1 + 1-1-1-1
-100MB = 16-16-16-16 + 4-4-4-4 + 4-4-4-4 + 1-1-1-1
-112MB = 16-16-16-16 + 4-4-4-4 + 4-4-4-4 + 4-4-4-4
-* 128MB = 16-16-16-16 + 16-16-16-16
-132MB = 16-16-16-16 + 16-16-16-16 + 1-1-1-1
-136MB = 16-16-16-16 + 16-16-16-16 + 1-1-1-1 + 1-1-1-1
-144MB = 16-16-16-16 + 16-16-16-16 + 4-4-4-4
-148MB = 16-16-16-16 + 16-16-16-16 + 4-4-4-4 + 1-1-1-1
-160MB = 16-16-16-16 + 16-16-16-16 + 4-4-4-4 + 4-4-4-4
-192MB = 16-16-16-16 + 16-16-16-16 + 16-16-16-16
-196MB = 16-16-16-16 + 16-16-16-16 + 16-16-16-16 + 1-1-1-1
-208MB = 16-16-16-16 + 16-16-16-16 + 16-16-16-16 + 4-4-4-4
-256MB = 16-16-16-16 + 16-16-16-16 + 16-16-16-16 + 16-16-16-16
-
-As you can see from the table, most configurations with 1MB chips
-in them can't be upgraded without throwing away chips.
-
-
-
-Here's some more about memory packaging.
-
-
-
-
-
-; DIP:
-
-
-Dual Inline Pack. These are the little 16-, 18- or more legged
-chips that looked vaguely like squared-off centipedes. Populating
-8Mb was a task for an evening. Obsolete, except for cache
-memory.
-
-; SIPP:
-
-
-Single Inline Pin Pack. These look like SIMMs, but have round
-in-line pins instead of the flat card-edge. Obsolete.
-
-
-; SIMM:
-
-
-Single Inline Memory Module. A small 30-pin card composed of
-several chips (the number differs by manufacturer, age, and
-density) and support components (mostly older modules) that
-installs in a snap-in socket. They evolved through 128K,
-256K, and 512K modules--all sadly obsolete today--into 1Mb,
-2Mb (rather rare), and 4Mb modules. Now generally superseded
-by...
-
-; 72-pin SIMM:
-
- Introduced in the last couple of years to cut down on the number
-modules needed, they usually run 4Mb, 8Mb, 16Mb, and 32Mb. Many
-motherboards are available with both 30 and 72-pin SIMM sockets
-to allow migration use of your older SIMMs.
-
-; DIMM:
-
- Dual In-Line Memory Module. This is the current cutting edge,
-available in 64MB and 128MB sizes.
-
-
-
-There are also adapter cards that will accept 30-pin SIMM
-modules and plug into a 72-pin socket; make sure you've the room for
-these if you intend to try them, as they protrude quite a bit above
-the board. There are also companies that will, for modest fees,
-desolder the memory chips from 30-pin SIMMs and wave solder them onto
-72-pin boards.
-
-
-
-(Thanks to Dave Ihnat for the glossary
.)
+Describe
[HowToUnixHardwareBuyerHOWTO
] here.
