Penguin
Annotated edit history of MFM version 5, including all changes. View license author blame.
Rev Author # Line
3 JamieCurtis 1 The proper name for this interface is actually ST-506/ST-412.
1 MarcelVanDeSteeg 2
3 This is a very old interface, used to connect storage devices to a motherboard.
5 CraigBox 4 This interface predates [IDE], and is not used anymore for harddrives. It was developed in the 1980's by Seagate, a storage technology company.
1 MarcelVanDeSteeg 5
6 Typical harddrive sizes are 5MB, 10MB and 20MB.
7
4 JamieCurtis 8 [MFM] actually refers to the encoding method used for storing data on the disk. [MFM] is an acronym for "Modified Frequency Modulation".
9 Another encoding method used with this interface is [RLL]. ([RLL] encoding is possibly still used on modern [IDE] drives)
1 MarcelVanDeSteeg 10
4 JamieCurtis 11 ST-506/ST-412 cables look like skinny [IDE] cables. (About half the width?) A single ST-506/ST-412 harddrive needs two cables, one is 20 pins, the other is 34 pins.
1 MarcelVanDeSteeg 12
13 The biggest problem with this interface[1] is that there is no logic board mounted on the harddrive. The harddrive is controlled
4 JamieCurtis 14 by a separate controller card. Each harddrive requires its own unique controller card. Don't expect the controller cards to have any markings on them to indicate which harddrives they belong to/can work with. You have an ST-506/ST-412 harddrive but no controller card? Bad luck, use it as a boatanchor or a doorstop
1 MarcelVanDeSteeg 15 ----
16 Apparently floppy drives still use this protocol (with [MFM] encoding)
17 -----
4 JamieCurtis 18 ST-506/ST412 hardrives are BIG, NOISY, HEAVY and UNRELIABLE[2]. (About the size of a CD-ROM drive. They sound like typewriters IIRC :)
1 MarcelVanDeSteeg 19 -----
20 ''"The last time I fiddled with an [MFM] harddrive was about 15 years ago, so most of this is from memory and whatever I could quickly google up ;^)" -- [MarcelVanDeSteeg]''
21 ----
22
23 [1] Besides the slow speed and the small storage capacity of the harddrives :D
24 [2] I ran into a working example the other day, buried in the internals of an old 4Mhz 8088 XT.
25
26 CategoryHardware
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