I've just bought a Tyan S2466-4M Mobo, an Athlon XP 2400, and a 512Mb stick DDR of PC2100 memory (not registered) . I've installed then installed Dos 6.22 (yes DOS !
in order to get a PCB routing package running (Cadstar 7 - it doesnt run well under Windows).
The software puts the VGA into a 16 colour 640*480 graphics mode, and then runs OK, except for the fact that the characters are illegible. Difficult to describe, but basically instead of normal characters, it's just a random selection of dots. The software runs fine, and I can see all the PCB routes, pads, colours etc, just the text is unreadable.
I've tried 3 different AGP graphics cards (2 based on a GeForce 4 MX440, and one on an older ATi Rage II), and all three are the same.
It seems to me that the processor can't read the VGA character set properly. Either that or DOS/EMS doesn't like 512MB, and keeps putting data in memory it can't then access.
The software (Cadstar7) works well on other (non XP) Athlon machines using the same graphics cards, and up to 384MB, so I'm rapidly comming to the conclusion its either the MPX chipset, or possibly the XP processor. Trouble is, I don't have another machine with an XP processor in it to rule the processor in or out.
Anyone got any ideas?
Incedentally, I've also installed Windows 2000, and run Cadstar in a Dos shell, with identical results! I reverted to DOS to rule out any Win2K issues.