There is a bug involving the emulated Tseng Labs. ET4000 on PCem. I'm using a utility that came with the emulated Tseng ET4000 card called the Diagnostic Test Program (TVDIAG.EXE), a utility that tests the ability to select VGA, EGA, CGA or MDA modes. The VGA and EGA modes work, however when I try to select either CGA or MDA modes, I get this:
- TSENG ET4000 CGA-MDA.png (5.11 KiB) Viewed 4379 times
I don't know if the same issue happens on real hardware, but this needs to be fixed.
(On a side note, when the Tseng ET4000 is emulated on DOSBox, the CGA and MDA modes do work although I haven't thoroughly tested it.)
Hardware Tested
AMI386 based on the OPTI-495SX chipset
4 MB RAM
Tseng ET4000 w/1 MB display RAM