Super VGA and UNIX

[Pim Zandbergen]

It appears to be very difficult to program a VGA card
beyond standard modes on a System V/386 r 3.2 system.
Several people writing graphic libraries, GIF viewers
or X servers have shared their horror stories on the net.

What I understand is that the vendors don't provide ioctl's
for SVGA modes, and you can't use the VGA BIOS to do it 
for you either, resulting in having to access registers directly.
This requires very detailed information on the card (hard to get),
and is also very non-portable. Manufacturers discourage programmers
to access register directly, stating they will only provide
a consistent BIOS interface and may change register functionality
between revisions of their card.

I would be much easier if one could use the BIOS but I guess
this is impossible because of BIOS code being non-reentrant
and the processor running in protected mode.

But all DOS software *is* capable of doing this through VP/ix
as long as you comment out the VGAROM line in vpix.cnf.

So maybe it is possible to change the processor mode to
virtual mode, do a BIOS interrupt and then return to 
protected mode.

If someone could tell me whether this is possible,
or, even better, how to do this, I would be very grateful.
-- 
Pim Zandbergen                          domain : pim at cti-software.nl
CTI Software BV                         uucp   : uunet!mcsun!hp4nl!ctisbv!pim
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