Notes for Mach64 X Server Kevin E. Martin (martin@cs.unc.edu) 6 June 1995 1. Supported Cards, RAMDACs, and Bits Per Pixel The Mach64 X server supports 8bpp with a dot clock up to 80MHz on all Mach64 based cards. On certain 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 ATI68880 135MHz 8 1280x1024 2Mb ATI68880 135MHz 16 1280x1024 4Mb ATI68880 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 All Others[*] 80MHz 8 1280x1024 2Mb [*] - The dot clocks are limited to 80MHz and the bpp is limited to 8. The RAMDAC is reported when you run the Mach64 X server with the "-probeonly" command line option. The ATI68860 and ATI68880 RAMDACs are usually found on ATI Graphics Pro Turbo and ATI WinTurbo cards. The other RAMDACs are usually found on ATI Graphics Xpression cards. As advertised, Mach64 graphics cards can use a special 24bpp mode (packed pixel mode), but this is not currently supported in the Mach64 for various reasons. The main one is that there is no current support for 24bpp modes in the X Consortium's servers. Adding this support will require a great programming effort. 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. 2. Optimizing the speed of the Mach64 X server To maximize the speed of the Mach64 X server, I suggest that you use the following maximum resolutions. This will allow room for the font and pixmap caches and a hardware cursor. Max Resolution BPP Video RAM -------------- --- --------- 1280x1024 8 4Mb 1280x1024 16 4Mb 1024x767 32 4Mb 1280x1024 8 2Mb 1024x767 16 2Mb 800x600[*] 32 2Mb [*] - With a 2Mb video card, the only way to use the font and pixmap cache is to have a virtual resolution of 1024x480 with a 640x480 mode. I suggest using 800x600 to maximize your screen size at the cost of the speed gained from the caches. Technical explanation for the above suggestions: The Mach64 X server uses a font and pixmap cache that is only available at a screen width of 1024. This restriction will be removed in a future version of the X server. To obtain the best performance from your video card, you need to make sure that there is enough room off-screen for the caches (at least 1024x256). In addition to the cache, the Mach64 uses memory mapped registers which are mapped to the last 1024 bytes of the memory aperture. This takes away another line from video memory. Thus, you need at least a video memory area of 1024x257. 3. XF86Config options Several options are supported in the "Device" section for the Mach64 X server. The Mach64 X server reads the Clocks from the BIOS. The "Clocks" lines in the XF86Config file are normally ignored by the Mach64 X server unless the "no_bios_clocks" option is given. Option "sw_cursor" This option allows you to use the software cursor instead of the hardware cursor. Option "composite" This option will set the composite sync for monitors that require this. Option "dac_8_bit" This option enables 8 bits per RGB value. Note this option does not work with the Chrontel 8398 RAMDAC. Option "override_bios" This option allows you to specify a video mode that the video card's BIOS believes to be illegal. Some BIOSs have incorrect maximum resolution and/or dot clock limitations. Use this option with care. It is possible to specify a video mode that can damage your card. Option "no_block_write" This option allows you to turn off block write mode. Block write mode only works on certain types of VRAM cards, and this option has no effect on DRAM based cards. If you see noise on the screen that can be captured via xmag, then it is probably a problem with block write mode. This ``noise'' usually looks like bits of windows/menus repeated on the screen. Option "block_write" This option allows you to turn on block write mode. Block write mode only works on certain types of VRAM cards, and this option has no effect on DRAM based cards. If you want to override the probed default, you can use this option. Option "power_saver" This option allows the server to use the power saving features of certain "green" monitors instead of blanking when the screen saver is activated. This option is still experimental. Option "no_bios_clocks" This option allows you to override the clocks read from the video card's BIOS. Normally the Mach64 server will ignore the Clocks line, but with this option the clocks from the XF86Config file can override the BIOS's clocks. MemBase baseaddress This entry specifies the video memory aperture address. Normally the aperture address is automatically determined, but on some VESA Local Bus systems the address chosen will not work. If the Mach64 X server is dying with a seg. fault, then try setting the aperture address to another location. Generated from XFree86: xc/programs/Xserver/hw/xfree86/doc/sgml/Mach64.sgml,v 3.5 1995/07/21 14:40:46 dawes Exp $