Date:	Wed, 01 Mar 1995 08:24:24 -0500 (CDT)
From:	Aaron Ucko <UCKO AT VAX1 DOT ROCKHURST DOT EDU>
Subject:	Re: Graphics drivers
To:	A DOT APPLEYARD AT fs2 DOT mt DOT umist DOT ac DOT uk
Cc:	djgpp AT sun DOT soe DOT clarkson DOT edu
Organization:	Rockhurst College; Kansas City, MO

>  The only purpose of these graphics drivers seems to be to map the nine GO32
>screen modes (0 = 80*25 text, 1 = default text, 2 = CX*DX text, 3 = biggest
>text, 4 = 320*200 graphics, 5 = default graphics, 6 = CX*DX graphics, 7 =
>biggest non-interlaced graphics, 8 = biggest graphics) onto his PC's graphics
>chip's own screen modes (AH=0xff, AL=z, int10: go to GO32 screen mode z).
>  But there are ways that a program can for(n=0;n<255;n++) find what mode n is
>and what its details are, e.g. the SuperVGA interrupt `AX=0xf401, CX=n,
>ES:DI=array, int 10' writes into the array a lot of info re screen mode n.
>  In view of this, please can't Gnu C have one graphics driver only, that uses
>these find-screen-mode-info interrupts to find the graphics chip's modes? Thus
>all the miscellaneous horde of graphics drivers that clutters up djgpp could
>be pensioned off. For example Windows Setup can cope easily with different
>graphics chips without me having to tell it what graphics chip I have.

The builtin VESA driver uses these AX=4f01 interrupts for everything and
works reasonably well on most cards--as long as you have `nc 256' somewhere
in your GO32 enviroment variable.  The other drivers exist for purposes of
flexibility--if one of them works better, then you can use it.


--- Aaron Ucko (ucko AT vax1 DOT rockhurst DOT edu; finger for PGP public key) -=- httyp!
-=*=-Just because you're paranoid doesn't mean they aren't out to get you.-=*=-
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