We have had reports of the server failing to detect the amount of installed
memory and the correct dot-clocks on older TVGA8900 boards. If the server
fails to detect the correct amount of memory, use the "Videoram"
keyword in your XF86Config file to specify it.
(e.g. Videoram 512 or Videoram 1024). If
the server has problems detecting the dot-clocks, try adding the following
line to your XF86Config file:
Clocks 25 28 45 36 57 65 50 40
This line gives the clock values provided by older Trident clock synthesizer
chipsets. This also appears to be the standard first 8 clocks for the newer
clock synthesizers, but you should have no problems on newer boards.
Some newer Trident 8900B/C boards are apparently being built with the clock
synthesizers used on the 9000 and 8900CL boards. If your board has a chip
labeled "Trident TCK900x" ("x" has been seen as 2 or 4; there may be others),
your board may actually have a 4th clock select bit. The 9002 has twelve
distinct clocks (the other 4 are duplicates); the 9004 has 16 clocks (the
same 12 as the 9002 + 4 others). If you see such a chip on a board with
an 8900B or 8900C, put the following line in the Device section of your
XF86Config file:
Option "16clocks"
This will cause the same clock selection code as is used for the 8900CL to
be used for the board.
While developing the Trident driver, an interesting and perturbing hardware phenomenon was discovered. When using the default board jumper configuration, dot-clocks above 57Mhz would frequently lock up the machine. There appear to be jumpers on all of the Trident boards that determine whether the board will operate in zero-wait-state mode on the ISA bus. Disabling the zero-wait-state mode via jumpers cured the lockups, but at the expense of performance. Whether or not a given system will experience this problem is likely a combination of (a) bus speed, (b) video memory speed, and (c) dot clock speed. So be prepared for this phenomenon to occur, and have the board documentation handy.
NOTE: VLBus cards are also subject to the above. By specifying the Clocks
in the XF86Config file, these lockups are overcome. But it may
be worth checking wait states etc. on the card and in the BIOS setup.
$XFree86: xc/programs/Xserver/hw/xfree86/doc/sgml/trident.sgml,v 3.22.2.9 1999/06/25 08:57:15 hohndel Exp $ $XConsortium: trident.sgml /main/11 1996/10/28 04:24:08 kaleb $