First post, by dosgamer
I noticed some weird color glitches in a few games. The games so far are: Midwinter 1 and 2, Civilization 1 (tried rev. 1 and rev. 5), Comanche Maximum Overkill.
As you can see, some colors (mostly black/darker colors?) are replaced with various shades of red.
My System: Dell 486DX33 w/16MB RAM (with parity), 2GB CompactFlash Card, WD90C30 VGA on board, 1 MB VRAM (512k on board + 512kB on upgrade module), MS-DOS 6.22. ISA cards installed: Creative CT1600, 3com Etherlink III Combo with 8kB EPROM containing XTIDE BIOS, Roland LAPC-I. PSU is a LiteOn 224W model that is actually intended for a bigger machine. Voltages check out and nothing suspicious inside. Caps are all high quality Nippon Chemi-Con.
Things I tried:
- enable/disable VGA IRQ
- enable/disable VGA ROM shadowing
- different main memory modules
- remove 512kB VRAM board
- tested VRAM using Amidiag, reports no errors
- tested main memory using Memtest86, no errors
The glitches go away if I either slow the computer down using a BIOS setting (changing "CPU Speed" from "33MHz" to "Compatible", but I think it doesn't actually change the CPU speed but uses wait states instead) or set the CPU clock jumper on the motherboard to 16MHz. At 25 and 20 MHz, glitches are still there. Also, Comanche looks fine after I install the Pentium update.
All other games work fine (much older and newer ones, e.g. Might & Magic I, Wizardry VI, Stellar 7, Panzer General, Master of Orion 2, Raptor, Blackthorne). Windows 3.11 works fine.
Anyone have an idea what's going on? I remember playing Civ on my 486DX2-66 back in the day without problems, so it can't be the CPU speed.
Coppermine Celeron 800 @ 1.12GHz (8x140) - Asus P2B Rev. 1.12 - 256MB PC133 CL2 - Voodoo5 5500 AGP - SB AWE64 CT4520 - Roland SCC-1 - Intel Pro/1000GT - 1.44MB Floppy - ATAPI ZIP 100 - 120GB IDE - DVD-ROM - DVD-R/RW/RAM - Win98SE