From:	"Damian Yerrick" <snews AT pineight DOT 8m DOT comMUNIST-PIGS-AOL>
Newsgroups:	comp.os.msdos.djgpp
References:	<F77915E7F086D31197F4009027CC81C917B595 AT probe-2 DOT as-london DOT acclaim DOT com>
Subject:	Re: Allegro, VESA - help
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Organization:	Pin Eight Software <http://pineight.8m.com/>
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Date:	Tue, 04 Jan 2000 19:50:51 GMT
To:	djgpp AT delorie DOT com
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"Shawn Hargreaves" <SHargreaves AT acclaimstudios DOT co DOT uk> wrote:
> Allegro actually makes another simplification of the banking system:
> it requires that bank switches not occur in the middle of a scanline.
> That hugely simplifies all the drawing code, and is no problem on
> cards with overlapping banks, but it means that for cards where the
> banks don't overlap, I have to fiddle with the screen dimensions to
> avoid a switch coming in the wrong place. That's why on some cards,
> even when you ask for a 640x480 screen, Allegro will actually set
> a 1024 pixel wide virtual display. Wastes video memory for the sake
> of much simpler and faster drawing code.

And requires twice the video RAM for 800x600 at a given depth.
For example, 800x600 normally needs only 1 MB at 16-bit depth;
it needs 2 MB with the Allegro system. But I'm not complaining.

--
Damian Yerrick    http://yerricde.tripod.com/
View full .sig:  http://www.rose-hulman.edu/~yerricde/sig.html










xg2 sucked big 1s...
...i play mario kart and ctr.

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