Date:	Wed, 5 Jan 1994 22:26:30 -0500 (EST)
From:	David Max <max AT SLINKY DOT CS DOT NYU DOT EDU>
Subject:	Using VESA for SVGA high-res double buffering.
To:	DJGPP <djgpp AT sun DOT soe DOT clarkson DOT edu>

   I recently looked into how to do double buffering under graphics modes
that don't support multiple pages under standard VGA. I was actually
surprised to find out that this is supported under VESA. For example, with
a 1 Meg SVGA card you can do two pages of 1024x768x16, 800x600x256, or
640x400x32K. You can even do other effects such as smooth scrolling or
having a 640x480 window onto a 1024x1024x256 virtual screen. 
   All these effects were demonstrated on my card using packages I 
downloaded from Simtel. One package is a VESA VBE TSR, and the other was 
a library for Borland C/Microsoft C to call the VESA routines. Can 
DJGPP/LIBGRX use this kind of VESA interface? I know there is a .grn 
driver for VESA that I haven't tried out yet, but don't virtual 
screens and page flipping go beyond vesa.grn?
   For those who are interested, the packages are on Simtel in the 
graphics directory:
   univbe42.zip   Universal VESA Video BIOS Extension TSR
   svgakt42.zip   SuperVGA kit library for VESA SuperVGAs

David Max

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