Mail Archives: djgpp/1997/05/10/14:03:54
Mitchell Spector writes:
>How does one go about programming support for non-standard video modes?
>(I'd like 512x384 with 8-bit color, implemented so that it's useable by
>Allegro.) UniVBE is able to do this even when using video cards that
>ostensibly don't support that resolution, and I'm curious how this can
>be done.
UniVBE does it by having lots of very chipset-specific code for each
card that it supports: not a realistic option for most people!
It is possible to get quite a lot of non-standard VGA modes by entering
mode-X and tweaking the VGA register settings, but I've never heard of
512x384 being accessible in this way (certainly modes like 360x480,
376x282, and 400x600 are quite possible, even if they don't work on
every monitor). To see how these are done, look at the modex.c file from
Allegro. It enters standard mode 13h and then tweaks the appropriate
registers, using some tables that list the changes required for each
video mode.
>Thanks in advance for any pointers to documentation or other
>information.
Get VGADOC3 from x2ftp.oulu.fi (I can't remember the exact path, it's in
something like /pub/msdos/programming/docs).
--
Shawn Hargreaves - shawn AT talula DOT demon DOT co DOT uk - http://www.talula.demon.co.uk/
Beauty is a French phonetic corruption of a short cloth neck ornament.
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