I would like to report a issue regarding the Tseng ET4000AX and the Trident 8900B/D graphics cards - certain video emulation modes either throw display corruption or produce a blank screen.

First of all, the Tseng ET4000AX, I use a utility called the Diagnostic Test Program (TVDIAG.EXE found in the C:\ET4000 directory). The utility gives you options to test the video adapter, set VGA, EGA, CGA or MDA modes. Here's a screenshot of the utility in EGA mode:

When I press either C (Set CGA Mode) or M (Set MDA mode), the screen goes blank until I either press V (Set VGA Mode) or E (Set EGA mode). This utility was tested on the DataExpert MB-495SX (AMI 486).

Next, it's the Trident 8900B/D graphics cards. The graphics card include a utility called Set Video Modes for Trident VGa/GUI (SVM.EXE utility can be found in C:\TVGAUTIL\UTILITY directory).

The utility has options to set different video modes to either VGA, EGA, CGA and Hercules. For TVGA Extended Modes, options include Text Mode, 16 colour, 256 colour or HiColor modes.

Here's a screenshot of the utility:

Selecting any CGA mode (including Warm Boot) only produces a black screen. Selecting HERC mode (80x25-2) gives you this:

HiColor modes don't seem to work correctly with this utility when it's emulated under 86Box. Here are example screenshot outputs:

1. 320 x 200 @ 24bpp

2. 640 x 480 @ 24bpp

3. 800 x 600 @ 16bpp

4. 800 x 600 @ 15bpp

Other modes work correct as it should. This utility was tested on the Award U-BOARD 486 (award486) machine.

Please look into this issue on what could be causing these modes to not work correctly or not at all.

Thank you. :)