From:	"Joel_S" <jbs30000 DOT news DOT invalid AT web2news DOT net>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: VGA DAC programming
Date:	Tue, 14 Jan 2003 14:44:52 +0100
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To:	djgpp AT delorie DOT com
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Reply-To:	djgpp AT delorie DOT com

Great, I'll give it a try.  Thanks, I appreciate it.
> Check the values of the ATC Palette values.
> Believe it or not, all VGA modes, except 8-bit or higher,
> use *both* the ATC
> Palette and the RAMDAC Palette.
> The reason that it works under BASIC is that BASIC sets
> all of the ATC
> palette
> values to their indexes.
> However, INT 0x10 does not do so.
>
> If you don't believe me, try the following BASIC code:
>
> SCREEN 12
> FOR N=0 TO 15
>     LINE (N*20,0)-STEP(19,100),N,BF
> NEXT
> SLEEP
> FOR N=0 TO 15
>     X = INP(&H3DA)
>     OUT &H3C0, N
>     OUT &H3C0, RND * 64
> NEXT
> X = INP(&H3DA)
> OUT &H3C0, &H20
> X = INP(&H3C0)
> X = INP(&H3DA)
> SLEEP
> END
>
> This should first produce the expected colour bars, then
> after pressing a
> key, change the colours to random ones.
>
> Try the following code:
> {
>     char n, x;
>     for (n=0; n<16; n++){
>         x = inportb (0x3DA);
>         outportb (0x3C0,n);
>         outportb (0x3C0,n);
>     }
>     outportb (0x3C0, 0x20);
>     x = inportb (0x3C0);
>     x = inportb (0x3DA);
> }
>
> Hope this helps.
>

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