DOS/4G and DOS/4GW FAQ:
Video Support

1. Can I under Windows XX switch between screen resolutions like 800x600 and 1024x768?
2. Does DOS/4G automatically translate VESA extensions?

1. Can I under Windows XX switch between screen resolutions like 800x600 and 1024x768?

DOS/4G doesn't use the graphic screens at all -- our tools are strictly text mode. We do nothing to interfere with the user's program using whatever graphics resolutions they can.

So the answer is: if you can do it in real mode, you can do it in DOS/4G!

2. Does DOS/4G automatically translate VESA extensions?

No. While DOS/4G automatically handles most basic interrupt 10h video functions, so that you can issue them from protected mode, we do not translate the parameters to the interrupt 10h VESA extensions.

You can, however, call the VESA BIOS directly by using the DPMI interrupt 31h/300h (Simulate Real Mode Interrupt) to call these functions. You also may want to look at the FAQ on converting linear addresses to real mode addresses (since any address passed to the VESA must be a real mode address pointing to memory below 1MB).