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From: eli@smectos.gang.umass.edu (Eli Brandt)
Newsgroups: comp.graphics
Subject: Re: 64K colors?
Message-ID: <30124@dime.cs.umass.edu>
Date: 6 May 91 19:04:42 GMT
References: <1991May2.001518.30298@kuhub.cc.ukans.edu> <10497@labtam.labtam.oz>
Sender: news@dime.cs.umass.edu
Reply-To: eli@smectos.CS.UMASS.EDU (Eli Brandt)
Organization: University of Massachusetts, Amherst
Lines: 39

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.

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