roell@informatik.tu-muenchen.de (Thomas Roell) (03/21/91)
As perhaps some of you know, there are three different Color Lookup Tables
built onto a VGA boards. They all differ in the number of bits that are used
to specify a color:
471/171: 8 bits per gun
476/176: 6 bits per gun
478: 6/8 bits per gun
Normally you'll find on a VGA the 476/176. But there are some new boards
(Orchid Prodesigner II) that use the 478. As I saw from the pinout there is
one pin responsible to switch between 6 and 8 bits per gun.
So far so good. But there also seem to be the possibilty to switch modes
without hardware assistance by writing a specific io-sequence to this chip.
This is what happened to some users of X386 while displaying gif-pictures
with xloadimge.
My question is now: Has someone informations about this chip, and how can I
exactly switch modes (not by accident as with xloadimge) ?
Another topic is that I whatched on the CeBIT a VGA that uses a special
CLUT (from Sierra) which can do 32768 colors (truecolor). Where can I get
this CLUT & docs ?
- Thomas
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