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From: jrd@cc.usu.edu
Newsgroups: comp.os.msdos.programmer,comp.graphics
Subject: Re: Double Buffering on a ATI VGA Wonder
Message-ID: <1991May27.162620.47918@cc.usu.edu>
Date: 27 May 91 16:26:19 MDT
References: <1991May20.063352.1561@kessner.denver.co.us>
Organization: Utah State University
Lines: 39

In article <1991May20.063352.1561@kessner.denver.co.us>, david@kessner.denver.co.us (David Kessner) writes:
> Here is the story...  I have a 512K ATI VGA Wonder board and have written
> several routines to support it's 256 color modes-- like a blindingly 
> fast line drawing function.
> 
> I am doing rather complex 3-D animations and have also been very
> sucsessful at that also.  (I've been rotating a wire frame couch at
> 26 frames/sec, amung other things-- using floating point even!).
> 
> What I need now is how to double buffer the display.  What I'd like to do
> is use a 640x400 display mode (which uses almost 256K of RAM) and divide
> the video RAM into two logical "screens".  Then display one while drawing
> on the other.  Sounds simple enough.  While I have been doing graphics
> for quite some time, VGA programming is another thing-- but I am not
> afraid to get my hands dirty with some assembly...
> 
> So, how do I do this?  BIOS Calls?  VGA Register programming?  (I am also
> not afraid to make this ATI VGA Wonder specific-- read on.)
> 
> While code fragments would be nice, an answer like, "Look up INT 10h
> Function ??, etc" would suffice quite nicely...
> 
> While on the subject... This program(s) are really for my own amusement
> and learning-- but if you happen to own a 512K VGA Wonder and a math
> chip (386 prefered, as well as an IIT 3c87 FPU) I'd be willing to share
> what I have-- which is minimal but could spin store logo's for you...
> 
> -- 
> David Kessner - david@kessner.denver.co.us            |
> 1135 Fairfax, Denver CO  80220  (303) 377-1801 (p.m.) | Reunite PANGEA!
> Why can't everyone have three or four line .sig's?    |
---------------
David,
	And the answer is... register twiddling. If your vendor doc's are
inadequate for the purpose then one book worth buying is "Advanced Programmer's
Guide to SuperVGAs" by George Sutty and Steve Blair, Brady/Prentice Hall, 1990.
Recall that those extra 256KB are well hidden out of the way with vendor-
specific techniques. Hence the register stuff.
	Joe D.