From: "Damian Yerrick" <mail DOT me DOT at DOT your DOT own DOT risk AT pineight DOT 8m DOT com>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Screen Address in VESA 2.0
Date: Tue, 14 Sep 1999 18:58:47 -0500
Organization: Rose-Hulman Institute of Technology
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JAB <jab_joe AT my-deja DOT com> wrote in message
news:7rmff2$5rt$1 AT nnrp1 DOT deja DOT com...
> Hiya
>
>  I've written a 3D thing on my dear old StrongARM RPC.

That's the same CPU that Apple used in Newton.

> Now I'm converting it over to the PC, compiling it with
> djgpp. I've got code to change to the screen mode I want
> (640 by 480 in 32 bit) but I can't get the screen address to
> write to. On the Acorn you just get the screen address and
> start writing to it. I can't beleive that you need the pages
> and pages of code I'm told I need. Ploting to screen is
> simple; how can it be so hard on the PC?

The PC is a patched together system. Memory is all over
the place. VGA video memory used to be at absolute
address 0x000A0000 (formerly known as A000:0000);
SVGA card makers independently placed it at various
positions and folded it in weird ways to fit into the address
space of the PC; now VESA provides a way to get at the
memory.

> There must be a way of getting the screen address,
> unlocking it from it's protection, and get on with the bloody
> thing. My question is how? How can I get just the screen
> address and unprotect it for use?

Allegro, a driver library by Shawn Hargreaves et al.,
can access VESA 2. Get the source at
http://www.talula.demon.co.uk/allegro/
Look at Allegro; then come back to C.O.M.D

Damian Yerrick
http://come.to/yerrick
http://pineight.webjump.com