[Coco] What do you make of this non-approved HSCREEN mode?

[jdaggett at gate.net]

On 14 Jun 2009 at 22:25, Torsten Dittel wrote:

> Could you (or someone else) help my weak memory (and prevent me from
> Googling the whole night): what was exactly the difference between the
> '86 and the '87 GIME? I know the '86 had one or more bugs which have
> been fixed in the '87 run. Wasn't that related to hardware scrolling
> somehow? Is there software, which will only run on '87 GIMEs for that
> reason? What happens if you use that software on a '86er? Could you
> imagine a way to detect the GIME version by software or user
> interaction (e.g. "If you can read this, you seem to have a new GIME
> version, press 'Enter' to continue").

Outside the obvisous that Tandy changed vendors for the GIME between the 1986 and 1987 
production run, there is no real way to tell what was changed. It may very well have been 
that the 1986 vendor did not have fab capacity and/or issues in manufacturing like yield 
issues. 

Never the less the 1987 parts seemed to fix sparkleis and some other minor issues. The 
occasional sparkles on the display could be attributed to the address mux that switches the 
lines between video and CPU access to the memory. The timing is very critical in that area 
of operation. 

james