Date: Mon, 3 May 93 23:03:01 CDT
From: csaba AT vuse DOT vanderbilt DOT edu (Csaba A. Biegl)
To: WKIM AT vms DOT cis DOT pitt DOT edu
Subject: Re: BCC2GRX patch 3 (?)
Cc: djgpp AT sun DOT soe DOT clarkson DOT edu

>> Questions about 256 color modes.

Since you are having problems with the 256 color mode even in 320x200
and using stdvga.grn, this the the only thing I can think of:

The preliminary GRX 1.03 I sent to Hartmut contains a new feature to
speed up 256 color drawing. For horizontal line fills (filled rectangles,
polygons, circles, etc...) it puts the VGA into a mode X-like planar
256 color mode. In this mode writing a single byte can set four pixels,
which will make the 256 color modes almost as fast as the 16 color ones.
The rest of the drawing is still done in the regular linear memory
mapping mode (lines, characters, etc..). In the final 1.03 release
I intend to make the use of this feature controlled by a driver flag.
Currently it is used unconditionally (remember, this is a preliminary
working version), which may cause problems on
some cards. (I tested it on Tseng and Trident cards until now.) 

As a temporary fix on incompatible VGA-s you can compile and link in
two modules from the 1.02 distribution: p8pixrow.o and p8pixblk.o.
If the linker sees these two modules BEFORE it sees libgrx.a then 
there will be no code in the program which tries to use the planar
256 color mode.

Csaba