I'm running my emulator with a copy of the int 10h service of dosbox, although some types converted to my emulator's types. I've based my VGA emulation on the FreeVGA specs and IBM documentation.

I'm trying to get all video modes working (00-13h), but atm only mode 2/3 and the 16/256/mode 0xF color modes seem to work, still fixing bugs in my VGA emulation.

I'm wondering though... How compatible is dosbox's interrupt 10h VGA i/o compared to the IBM VGA BIOS/int 10h? Are all register output (Sequencer/Attribute controller/DAC/CRTC) done the same way? If I would run it against a real IBM VGA, would it generate exactly the same output, neatly centered on the screen?

I'm running the screen using the CRTC specified output and stuff doesn't get centered or displayed correct (atm mode 6h is a blank screen and modes 4/5h give me about 1/4th a screen, with junk at random pixels (data from the high planes which are supposed to be cleared in VRAM during mode set?) And mode 0/1 is giving me about 1/2 text screen with double height characters. About 20x12 character clocks as far as I remember atm. Aren't modes 2/3/7 and 0/1 about the same, except double characters horizontally?