Re:non-standerd Vga Modes

 BBS: Inland Empire Archive
Date: 05-19-92 (03:46)             Number: 133
From: RICH GELDREICH               Refer#: NONE
  To: MARTIN BOUCHARD               Recvd: NO  
Subj: Re:non-standerd Vga Modes      Conf: (2) Quik_Bas

>
> Can the 360 X 480 mode can be BLOADed and BSAVED like 320 X 200 mode?.
> If yes, what is the begining segment of the screen in 360 X 480. Also,
> do you have some routines for clipping (like PUT & GET) the screen in
> that resolution. If not, I could allways make one in ASM.
>
> Bye,
> Martin Bouchard

    Yes, the 360x480 mode can be BSAVEd & BLOADed like any other VGA
screen. You must enable each plane one at a time and write out 43,000
bytes to disk. The entire image would take up a whooping 172,000 bytes
or so! I'll throw something together...
    The organization of the 360x480 mode is quite different from the
normal BIOS modes. Each address actually addresses 4 pixels- not one.
Since there are 4 planes, this makes things quite easy to understand.
Each line in the 360x480 mode is organized like this:

pixels   * * * * * * * * * * * * * * * * * * * * * * * * *
plane    1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 ...

    A pixel's address is:

    Address=(Y*90)+(X/4)

    and a pixel's plane is:

    Plane=(X and 3)

    Thanks to the VGA, any combination of planes can be written to at
the same time.

    I hope that helps out some- check out the source code to my setline
routine in the GIF decompressor for some working code(I also posted a
documented version of the assembly listing; see if you can find it).

I'll make a 360x480 mode screen saver & loaded and post it for you very
soon.

    Rich Geldreich

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