The Mach64 X server supports 8bpp with a dot clock up to 80MHz on all Mach64 based cards. On most cards, higher dot clocks and additional depths are available (see the table below). What determines this support is the RAMDAC on your card.
RAMDAC Max Dot Clock BPP Max Resolution Video RAM Required
-------- ------------- --- -------------- ------------------
ATI68860 135MHz 8 1280x1024 2Mb
ATI68860 135MHz 16 1280x1024 4Mb
ATI68860 80MHz 32 1024x768 4Mb
ATI68875 80MHz 32 1024x768 4Mb
CH8398 135MHz 8 1280x1024 2Mb
CH8398 80MHz 16 1024x768 2Mb
CH8398 40MHz 32 800x600 2Mb
STG1702 135MHz 8 1280x1024 2Mb
STG1702 80MHz 16 1024x768 2Mb
STG1702 50MHz 32 800x600 2Mb
STG1703 135MHz 8 1280x1024 2Mb
STG1703 80MHz 16 1024x768 2Mb
STG1703 50MHz 32 800x600 2Mb
AT&T20C408 135MHz 8 1280x1024 2Mb
AT&T20C408 80MHz 16 1024x768 2Mb
AT&T20C408 40MHz 32 800x600 2Mb
3D Rage II 170MHz 8 1600x1200 4Mb
3D Rage II 170MHz 16 1600x1200 4Mb
3D Rage II 170MHz 32 1024x768 4Mb
3D Rage II+DVD 200MHz 8 1600x1200 4Mb
3D Rage II+DVD 200MHz 16 1600x1200 4Mb
3D Rage II+DVD 200MHz 32 1024x768 4Mb
Rage Pro 230MHz 8 1600x1200 8Mb
Rage Pro 230MHz 16 1600x1200 8Mb
Rage Pro 230MHz 32 1600x1200 8Mb
Internal 135MHz 8 1280x1024 2Mb
Internal 80MHz 16 1024x768 2Mb
Internal 40MHz 32 800x600 2Mb
IBM RGB514 220MHz 8 1600x1200 2Mb
IBM RGB514 220MHz 16 1600x1200 4Mb
IBM RGB514 135MHz 32 1024x768 4Mb
All Others[*] 80MHz 8 1280x1024 2Mb
[*] - The dot clocks are limited to 80MHz and the bpp is limited to 8.
The table above specifies the maximum resolution and the video memory required to run this maximum resolution. Smaller resolutions will require less video memory.
The RAMDAC is reported when you run the Mach64 X server with the
"-probeonly" command line option. The RAMDAC reported should
be correct for all Mach64 cards. It can also be specified in the
XF86Config file, but this is not recommended unless the RAMDAC
reported in the probeonly output is incorrect. Before specifying the
RAMDAC in your XF86Config file visually verify which RAMDAC is on your
Mach64 card. If the RAMDAC reported in the probeonly output is
definitely different than what you see on the card, then check to see
if you have a RAMDAC specified in your XF86Config file. If you do,
comment this line out and re-run the Mach64 X server with the
"-probeonly". If it still reports the incorrect RAMDAC,
please send in a bug report to XFree86@XFree86.Org.
The ATI68860 RAMDACs are usually found on ATI Graphics Pro Turbo and ATI WinTurbo cards. The IBM RGB514 RAMDAC is found on the ATI Graphics Pro Turbo 1600 card. The other RAMDACs are usually found on ATI Graphics Xpression, ATI Video Xpression and ATI 3d Xpression cards. Mach64 CT, ET, VT, VT3, VT4, LT, GT (3D Rage), 3D Rage II, 3D Rage IIC, 3D Rage II+DVD, Rage Pro, and Rage LT Pro chips have an "Internal" RAMDAC (i.e., it is built into the Mach64 chip).
As advertised, Mach64 graphics cards can use a special 24bpp mode (packed pixel mode), but this is not currently supported in the Mach64 X server. This will be added in the next major release.
The Mach64 X server requires the video memory aperture to function properly. This means that ISA Mach64 cards in systems with more than 12Mb of main memory will not work. If you have a PCI based Mach64 card or a VLB based Mach64 card, then the Mach64 X server will work with any amount of main memory.
Accelerated doublescan modes are supported on VT, VT3, VT4, LT, GT, Rage II, Rage IIC, Rage II+DVD, Rage Pro and Rage LT Pro based Mach64 cards. Mach64 cards with other chips cannot handle accelerated double scan modes due to a hardware limitation. Non-accelerated doublescan modes should work with the ATI driver in the SVGA X server for all Mach64 cards.