[Coco] Hidden 256-color mode

Nickolas Marentes nickma at optusnet.com.au
Thu Jul 28 15:53:18 EDT 2005

James wrote:
Running out of pins on the GIME doesn't make sense. However, if they 
were tacking the mode onto the prototype, they very well could have run 
out of pins somewhere and running a line from somewhere indicating a 
certain state is certainly feasable to activate it.

Nick replies:
The "running out of pins" comment may not be totally accurate. My 
contact at Tandy who was quite high up in the chain and responsible for 
the CoCo3 (he called himself the father of the CoCo3), wasn't an 
engineer. He was more management I believe. He said "pins" but maybe 
what he meant was "registers". This makes more sense.

Maybe Al should lend the protoype board to one of the members on this 
list who has a good electronics background so as to analyze it up close. 
If this is not possible, we must get Al to at least remove the stickers 
on chips and take more close up photos of the prototype board. Anyone 
heard from Al lately?

The prototype could very well have the mode installed but it may not 
have translated to the production chip. It could be implemented fully in 
the prototype but was restricted in the production version due to "not 
enough pins". All I know is that my contact at Tandy claimed to have 
turned the mode on using one of the early CoCo3 production models...I 
would therefore assume a 1986 GIME chip. I know this version of the GIME 
had "bugs" in it that were corrected in the next 1987 revision. Maybe 
these bugs were inherited because of the inclusion of the 256 mode?

Why would a company invest a lot of money to release a second revision 
of a custom chip such as the GIME unless the problems were truly severe 
enough to warrant it? The CoCo3 was aimed at being a low cost computer 
and lowering costs was a high priority in order to remain competative. 
As we can see, the 1986 GIME was not so bad that the computer could not 
be used. Many of us are using '86 GIME chips today with no real 
problems. Certainly, no problems that can't be gotten around externally 
via software or via specific brands/speeds of RAM chips.

The only other people I suspect may that have some knowledge of this 
mode were the people/programmers at Spectral Associates. They were 
commisioned by Tandy to write some of the first CoCo3 specific software 
and they wrote the two CoCo3 Tandy Demo programs. These people got the 
early design and programming information from Tandy in order to achieve 
this so there is a good chance someone from there may have some 
knowledge of this mode. Does anyone know of anyone who worked as a 
programmer at Spectral Associates?

Nick Marentes

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