Message-ID: <33FE374E.3936@oregoncoast.com>
Date: Fri, 22 Aug 1997 18:05:18 -0700
From: Rudy Gingles <spy AT oregoncoast DOT com>
Reply-To: spy AT oregoncoast DOT com
Organization: Atek Systems
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Newsgroups: comp.os.msdos.djgpp
Subject: Re: Moving data from video memory to main memory?
References: <19970820025301 DOT WAA12569 AT ladder02 DOT news DOT aol DOT com>
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DrumC96 wrote:
> 
> Hey everybody,
>       I'm trying to figure this out. I wrote a blit function for svga that
> is pretty fast  moving dwords at a time when possible. I made a copy
> routine that is pretty much exactly the same except the bitmap destination
> is edi and the source in video memory is esi (which is opposite for the
> blit). I have a selector for video memory. The problem is, I can change es
> in a function and have no problems, such as call movsd and having data
> moved to video ram. When I change ds  to my video memory selector, I can't
> use movsd to copy data to main memory from video memory without a gpf.
> Please explain why and how I can get around that. If you can understand
> what I just tried to explain, then you probably have an answer. Im using
> nasm so please if at all possible us intel syntax.
> Sincerely,
> DrumC96 AT aol DOT com

Perhaps GCC is using DS to access your main memory?

Rudy