From:	Shawn Hargreaves <Shawn AT talula DOT demon DOT co DOT uk>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: lword moves to/from video buffer fail
Date:	Thu, 27 Mar 1997 19:18:34 +0000
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Distribution:	world
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To:	djgpp AT delorie DOT com
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Vik Heyndrickx writes:
>My question is whether lword (double word) memory access instructions
>can/should be used to address video memory. In my case, this produces
>problems: sometimes data isn't written at all, sometimes it ends up at
>the wrong place in video memory. Usually, I don't have any problems with
>my video card at all.

A very interesting question. Allegro makes extensive usage of 32 bit
moves to video memory (they are a _lot_ faster than 16 bit operations!)
and I've never had any trouble with them, or should I say that nobody
has ever complained about pixels going missing. 

I presume you are talking about text modes, from your comments about
Rhide: do similar things happen in graphics resolutions as well? If so,
does it make any difference whether you are in VGA 13h, mode-X, or an
SVGA resolution? And most importantly, what type of graphics card do you
have? I would be very interested in knowing more about this...


--
Shawn Hargreaves - shawn AT talula DOT demon DOT co DOT uk - http://www.talula.demon.co.uk/
Beauty is a French phonetic corruption of a short cloth neck ornament.

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