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From: junaid AT silas DOT cc DOT monash DOT edu DOT au (Mr A. Walker)
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Video question
Date: 1 Aug 1995 07:57:35 GMT
Organization: Monash University
Lines: 36
References: <DCL5Iu DOT 3M8 AT agora DOT rdrop DOT com> <3vjp2n$cg2 AT st-james DOT comp DOT vuw DOT ac DOT nz>
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To: djgpp AT sun DOT soe DOT clarkson DOT edu
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Malcolm Taylor (empty AT sans DOT vuw DOT ac DOT nz) wrote:
: Steve Havelka (shavelk AT agora DOT rdrop DOT com) wrote:
: : Hi.  I have written a few graphics programs (mode 13h) for DJGPP,
: : and they access video memory at 0xd0000000.  If I try to run

: Several ways. The above way is only possible on the 1.12m4 and earlier 
: version of djgpp in the nodpmi mode. The VRAM page fault handler is 
: specific to go32, so if you use dpmi you don't get these buffers. Djgpp 
: v2.0 is DPMI only, so you'll run into this problem if (when) you upgrade.
: buffers which can then be Blted to the screen. This is actually quite 
: fast in some situations (esp. when working with a slow video card).
: There is a hack available (I think) to do the page fault handling under 
: DPMI, but it isn't guaranteed to work.

	Hmm. Maybe you are confusing the near ptr hack with VRAM baank
switching. It might be possible to trap SEGV's exceptions in dpmi
and then look at the registers and do the bank switching in user
space. This may or may not work depending on the dpmi provider trapping
bad memory access in some 1M address space. It may or may not be hideously
slow depending on the exception handling response time.

I wonder how univbe52 does it during VESA VBE2.0 linear address bank
emulation? An indeed does it work at all under MS Win full screen?
From memory its shuts down windows with death() and resurect().


: Hope this helps.

: Malcolm

: : --
: : Steve
: : Life is pain.  -- Siddhartha

Junaid