[Coco] Hidden 256-color mode

[Nickolas Marentes]

Roger Wrote:
What if the software designers had to work only with the documented 
hardware features, meaning there would be no code in the ROMs for 
supporting a hidden 256-color mode...?

Nick Replies:
There is *definately* no code in the ROMS that support the *possibly 
hidden* 256 color mode. If there was, it would have been easy to find 
this mode. Also, Mark Hawkins (who was at PennFest 2000) would have 
known about the mode since he was involved with the Super ECB ROM. Mark 
was the one who found me the official Tandy R&D document that lists the 
mode. (see the doc on my web site). He found it at Microware's archives, 
same place Al found the CoCo3 prototype.



Robert wrote:
Isn't yyyyyrgb 1 byte per pixel? If not, is it 5 pixels on or off with 
the same 8 colors? Any chance the the "256mode" is a new semigraphics 
rather than PMODE type mode?

Nick replied:
What I was referring to was an RGB mapped 1 byte per pixel mode... 
something possibly along the lines of RRRGGGBB. The y component in 
yyyyrgb I think refers to intensity, which is normally associated with a 
composite signal I think. (RGB with 16 levels of intensity). This actual 
mapping could be wrong because my "contact" couldn't remember exactly. 
As for semigraphics mode, yes, it could be even that...but how to turn 
it on is the million dollar question.



Boisy wrote:
I wish you luck on that, Nick. I've been trying to get Allen to ship a 
HUGE box of old Microware disks to Tim Lindner for months now. If you 
find the secret that gets him to the post office, please let me know.

Nick replied:
Oh dear...that's not good. Al could be holding the key to the CoCo3's 
greatest secret. Even if the mode doesn't exist in production CoCo3's, a 
definate answer to this mystery is needed. It could even be that one of 
those disks may contain some test/experimental software that actually 
activates this mode...if it truly exists.