From:	Michal Mertl <xmerm05 AT manes DOT vse DOT cz>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: ALLEGRO - 256 shades of grey?? How?
Date:	Tue, 21 Oct 1997 11:29:12 +0200
Organization:	Prague University of Economics
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Message-ID:	<Pine.ULT.3.95.971021112307.28830B-100000@manes.vse.cz>
References:	<EI61FB DOT 4Bn AT cix DOT compulink DOT co DOT uk> <6269en$a32$2 AT news DOT ox DOT ac DOT uk> <199710171645 DOT MAA26299 AT delorie DOT com>
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On Fri, 17 Oct 1997, Alexander Bokovoy wrote:
>  Neither GRX nor Allegro is lying. 
>  Because standard VGA DAC specification is limited by 6 bits, 
>  VESA standard defines extended DAC register capacity. Peter use
>  800x600x256 mode which is not VGA mode but SVGA and exists only on
>  SuperVGA compliant videocards. Because old VGA cards are rare and we
>  all use SVGA-compatible cards this strange behavior of Allegro may be
>  explained by different implementation schemes in GRX and Allegro
>  palette manipulation routines (correct me if I wrong).
> 
I think you are not right that cards limited to 6bits wide DAC are rare. I
know most Cirruses, Tridents, S3s (except Virge I think) doesn't support
8bit. And DAC size is 6bits unless you tell it to be 8bit. 
I also think (but I'm not sure, so don't flame me for the second sentence)
that palettes in pictures are intended to be divided by 4 for 8bit display
(and will look ugly with 8bit DAC), only in true color you should use all
8bits.

Michal "MiMe" Mertl
  xmerm05 AT vse DOT cz

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