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From: daly@ecs.umass.edu (Bryon Daly, ECE dept, UMass, Amherst)
Newsgroups: comp.graphics
Subject: Re: 64K colors?
Message-ID: <13570.2825b4c2@ecs.umass.edu>
Date: 6 May 91 19:55:46 GMT
References: <1991May2.001518.30298@kuhub.cc.ukans.edu> <10497@labtam.labtam.oz> <30124@dime.cs.umass.edu>
Lines: 63

In article <30124@dime.cs.umass.edu>, eli@smectos.gang.umass.edu (Eli Brandt) writes:
> In article <10497@labtam.labtam.oz> graeme@labtam.labtam.oz (Graeme Gill) writes:
>>In article <1991May2.001518.30298@kuhub.cc.ukans.edu>, bbb@kuhub.cc.ukans.edu writes:
>>> Dear Net-ers:
>>> 
>>> ... and just today got my  
>>> Tseng Lab Inc. (TLI)  ET-4000 controller 
>>> data book.
>>> 
>>> While checking out the specs on the 
>>> 4000-chip, my eyes bugged as I saw that 
>>> it is (in theory anyway)  capable of 
>>> producing 65535 colors on screen using 2 
>>> bytes to produce a  pixel.
>>
>>	As I understand it, this is some sort of HAM (Hold And Modify) scheme
>>where the chip is put in a special mode, and certain colour values are reserved
>>as "instructions" to interpolation hardware to generate colours between two
>>of the available palette colours. This basically means that it is great for
>>specially written CAD packages that know how to use it for ant-aliased lines
>>etc., but it is not much good for general purpose use. (ie. If you want to
>>be able to set any pixel to any one of 65535 colours). It also has a dynamic
>>palette feature, that allows the palette to be re-programmed on the fly. One
>>only has to look at the difficulty people have had in using the Amiga HAM mode
>>to wonder how usefull all this stuff is. 
>>
>>	Graeme Gill
>>	Labtam Australia
> 
> I think you're thinking of Edsun's CEG DAC.  (Continuous Edge Generat*)
> The CEG is basically a plug-in replacement for the standard VGA DAC, in that
> it uses the same video-memory organization as VGA/Super VGA. ie, max 1 byte
> per pixel.  Tseng's ET-4000 is, I believe, a true 16-bit-color device, using
> two bytes for each pixel.  The CEG does indeed use some rather baroque
> HAMmy modes to do its smoothing; you embed special pixel sequences directly
> into the bitmap.  Please note that I've never seen either of these, and
> I know virtually nothing about Tseng's chipset.  Except that I *want* one.
> 
> /  Eli Brandt     eli@smectos.gang.umass.edu        32@4351 WWIV          \
> \  Mentally insert disclaimers               Mentally insert quote        /
> 
> 

I just heard that Diamond is releasing two new video boards based on the
Tseng ET4000 chipset.  The first is the Edsun CEG-based one.  (CEG=Continuous 
Edge Graphics).  The Edsun chip is more than a HAM scheme, and is actually a
DSP chip, from what I've heard, and does 64K colors, but not in a user
programmable way: You won't have 16-bit color to program.  Instead, the
chip automagically interpolates colors along edges, to eliminate aliasing, etc.
(Special programming is reqired, though!).  The Edsun chip is also a direct
replacement for the RAM DAC that is socketed in many current SVGA cards, but
the maximum resolution it handles is 800x600, and you would need drivers to
take advantage of its capabilities.  Diamond claims it's card will do its
stuff at 1024x768, and they seem willing to upgrade current SpeedStar owners
(like me! :) ).

The other board is called the Hi-Color, and they say it does 32K colors,
for real.  (15-bit color).  The price I saw on this one was $595 (from their
BBS).  I think max res was 640x480 at that number of colors, but I remember
no too much else about it.

-Bryon Daly
daly@ecs.umass.edu