For me, I'm currently running the Award SiS 496/497 machine (486DX2 @ 66 MHz with 64 MB RAM, Number Nine FX graphics card with 2 MB VRAM) for example. Text mode and ironically, Windows 3.11 in 1024 x 768 16-bit colours work without problems.
In the Settings menu, I select Video > Direct3D. When I do that, running a program that uses graphics will flicker and go black very frequently. If I select Settings > Video > DirectDraw, the display does not flicker at all.
In the emulated IBM PS/1 model 2011 (80286 10MHz w/16 MB RAM [15,488 KB usable], integrated VGA card), the same issue happens.
When I switch the machine configuration when using the Direct3D video mode, the display literally gets squashed and messed up:
This issue doesn't happen in DirectDraw video mode.
Also, when using the debugger version of PCem, looking in the pc.log file, I found a bit of information what could be causing the display to flicker and mess up:
Bad AT keyboard controller command A8
Bad AT keyboard controller command BC
Bad AT keyboard controller command BB
Bad AT keyboard controller command D2
Bad AT keyboard command 80
Set multiple mode - 16
INT out of range
The "INT out of range", "Double fault!", "Triple fault" error repeat in a infinite loop for a few seconds. That bug and the bad AT keyboard controller commands do not adversely affect the PC emulation at all.
I'm curious to ask here. Could this be a problem with the latest version of the drivers for my EVGA 8400GS 1GB DDR3 graphics card or a bug in the PCem emulation itself?