Hi Robin,

RS> DV>   I am running on a Pentium-S 120 with 32 megs EDO-RAM, a
RS> DV>   Virge-DX (S3) video card, and OS/2 Warp 4. Does this help??
RS> KK> Yes, a lot. but it means I don't know much about it since
RS> KK> most of my experience is in DOS and Windows. It may be the
RS> KK> same, for all I know. Does OS/2 still use the DOS video BIOS
RS> KK> interrupt 10h stuff? You may also need to get permission to
RS> KK> even access the video memory, as OS/2 may not want to share.

RS>   Yeah, access rights can cause headaches with pmode stuff, but a
RS>   well-designed OS should be able to recognize when a protection
RS>   fault is generated by something like reading/writing video memory,
RS>   or the interrupt vector table, and take appropriate action.

Err, Why?
There are preferred ways to access video memory directly under OS/2, but
they are intended for video device drivers and are fairly obscure. There
is an (obsolescent) way to access video memory directly via the VIO
system calls, but that restricts you to a single full screen window.

The preferred OS/2 way is to write the program as a Presentation
Manager (GUI) application in C (I _knew_ I could get on topic ) and
do the graphics manipulation via the OS/2 API (which is directly C
callable).

RS>   I might be wrong here, but isn't the video BIOS (save for patches
RS>   like VESA drivers for non-VESA video cards) in the video card ROM?
RS>   I don't think it's a DOS thing at all, though it is a PC thing.  He
RS>   should be able to use the video BIOS to set the mode and such.  I
RS>   thik the DOS video output routines (along with a lot of the rest of
RS>   DOS stuff) is accessed through INT 21h.

He's using OS/2, a protected mode OS. I don't know if the video BIOS is
written for protected mode, but I suspect it's real mode only so not
available in protected mode. The video BIOS is definitely a DOS thing,
you need drivers specific to each operating system to run it other than
under DOS. In the case of OS/2 they don't (normally) use any of the
existing BIOS code. Access to things via INT 21 is definitely a DOS
thing, OS/2 uses a completely different mechanism.

George

 * SLMR 2.1a * Computers eliminate spare time.

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