Generally, the ATI cards are not supported as well as Nvidia. If you are buying a new graphics card, you might be better off with an Nvidia, particularly with later model and higher spec cards.
But it is possible to get Radeon cards working. See notes at 
the DRI wiki and Radeon Linux howto.
The current Linux drivers can be downloaded from ATI's webpage.
For info on older drivers, see the page called RadeonOnNforce, which apparently solved a lot of problems for a lot of people.
ATI drivers are available in rpm form from the PenguinLiberationFront. (Although with my 9600 pro card, I found that the drivers from ATI gave 3d hardware acceleration, but the plf rpms of the same verion did not.)
Man, there's a lot of trouble geting drivers running on this. ATI Radeon Drivers for Linux with a link to a FC2 patch
See the excellent Gentoo Radeon FAQ. Gentoo's portage files for the radeon driver may also have a patch that helps you.
There is a a very good tutorial about installing ATI-drivers on Debian Linux.
Do you get errors like
/lib/modules/fglrx/build_mod/2.6.x/firegl_public.c: In function `__ke_get_vm_phys_addr': /lib/modules/fglrx/build_mod/2.6.x/firegl_public.c:1506: warning: implicit declaration of function `VMALLOC_VMADDR' make[2]: *** [/lib/modules/fglrx/build_mod/2.6.x/firegl_public.o] Error 1 make[1]: *** [/lib/modules/fglrx/build_mod/2.6.x] Error 2 make[1]: Leaving directory `/usr/src/linux-2.6.0-test11' make: *** [kmod_build] Error 2 [root@test 2.6.x]# modprobe fglrx Error inserting 'fglrx.ko': -1 Unknown symbol in module Oct 26 16:11:46 [kernel] fglrx: module license 'Proprietary. (C) 2002 - ATI Technologies, Starnberg, GERMANY' taints kernel. Oct 26 16:11:46 [kernel] fglrx: Unknown symbol VMALLOC_VMADDR Oct 26 16:12:14 [kernel] [drm] Module unloaded
You need to make a change to /lib/modules/fglrx/build_mod/2.6.x/firegl_public.c: add
#ifndef VMALLOC_VMADDR #define VMALLOC_VMADDR(x) ((unsigned long)(x)) #endif
to the beginning somewhere, and then cd .. back up to build_mod, run ./make.sh, cd back up to fglrx and run ./make_install.sh
There is a patch for this, and other issues, in Gentoo's ATI drivers portage tree.
(EE) fglrx(0): [agp] unable to acquire AGP, error "xf86_ENOMEM" (EE) fglrx(0): cannot init AGP (II) fglrx(0): [drm] removed 1 reserved context for kernel (II) fglrx(0): [drm] unmapping 8192 bytes of SAREA 0xd1a34000 at 0x40229000 (WW) fglrx(0): *********************************************** (WW) fglrx(0): * DRI initialization failed! * (WW) fglrx(0): * (maybe driver kernel module missing or bad) * (WW) fglrx(0): * 2D acceleraton available (MMIO) * (WW) fglrx(0): * no 3D acceleration available * (WW) fglrx(0): ********************************************* *
The problem is well documented - basically, you don't have correct AGPGART support. The way I solved this on LinuxKernel2.6 was to make sure UseInternalAGPGART was set to no in the XF86Config file and rebooting - if at any stage the fglrx AGPGART has loaded, you're shit out of luck. (Ask dmesg(8)).
If you have an NForce2; use Kernel 2.4.22 or higher for a kernel that supports the Nvidia AGPGART. (You should be using Kernel 2.4.24 or higher anyway!) It's native to 2.6.
With the NForce2 chipset there may be difficulties trying to have output mirrored to the TV out, unfotunately I do not currently know any solution other than to disable TV out support.
The Gentoo ATI Radeon FAQ has some great examples. If you're using a VIA KT400, start at Rage3D's message board.
With a 2.6.3 kernel I was getting a kernel oops everytime X tried to load with the fglrx module loaded. The backtrace looked something like this:
Feb 20 20:27:10 than kernel: Call Trace: Feb 20 20:27:10 than kernel: [<f89f49cb>] __ke_amd_adv_spec_cache_feature+0xb/0x80 [fglrx] Feb 20 20:27:10 than kernel: [<f8a031bc>] drm_agp_enable+0x0/0xc4 [fglrx] Feb 20 20:27:10 than kernel: [<f89fd2e8>] _r6x_CheckAGPCommand+0x130/0x178 [fglrx] Feb 20 20:27:10 than kernel: [<f89f4617>] __ke_agp_enable+0x17/0x40 [fglrx] Feb 20 20:27:10 than kernel: [<f8a03240>] drm_agp_enable+0x84/0xc4 [fglrx] Feb 20 20:27:10 than kernel: [<f89f513e>] firegl_ioctl+0x166/0x1a4 [fglrx] Feb 20 20:27:10 than kernel: [<c015b6d9>] sys_ioctl+0x219/0x270 Feb 20 20:27:10 than kernel: [<c0108cff>] syscall_call+0x7/0xb
A lot of Googling later, the fix that works for me was to find the function __ke_amd_adv_spec_cache_feature in /lib/modules/fglrx/build_mod/2.6.x/firegl_public.c and edit it so that it returned immediately; i.e. it should end up looking like this:
int __ke_amd_adv_spec_cache_feature(void)
{
return 0;
}
Save and exit, then cd .. back up to build_mod, run ./make.sh, cd back up to fglrx and run ./make_install.sh. Just removing the offending function might not always be a good idea, but doing this lets me use X with hardware acceleration, and I have yet to notice any issues.
There should be some shell scripts inside /usr/share/ati. One of them should remove the driver.
