pim@cti-software.nl (Pim Zandbergen) (09/30/90)
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@cti-software.nl CTI Software BV uucp : uunet!mcsun!hp4nl!ctisbv!pim Laan Copes van Cattenburch 70 phone : +31 70 3542302 2585 GD The Hague, The Netherlands fax : +31 70 3512837