[Color Computer] Re: [Coco] Hidden 256-color mode

[Mike Pepe]

OK, got the info. It's a fascinating read, but I've still got think that 
the 256 color mode is most likely not in the production GIME chip.

The "we ran out of pins" argument makes no sense. There are no external 
pins that have anything to do with video mode selection on the GIME at 
all. All selection is done with software. There are plenty of "reserved" 
and "unused" bits in the GIME address space, there's no reason in terms 
of address or packaging space that preclude the 256 color mode from 
existing.

The way you're supposed to enter this mode also makes no sense to me. 
Unless the designers intended this feature to never be discovered, 
there's no reason to make it so complicated. It may be some clever state 
machine hack, but again it seems illogical to make this mode's selection 
such a bizarre hack.

(However given some other odd design choices made with the GIME, it 
wouldn't entirely surprise me. Who thought it was a good idea to have 
two completly different color outputs? jeez.)

The third thing that comes to mind concerns the prototype versus 
production GIME. If the mode was in the prototype, yes, it may be in the 
production model. However disabling the feature on the silicon may be a 
simple matter of disconnecting or masking off a few gates in the 
production version. In short, disabling the feature doesn't strike me as 
requiring any significant effort.

It may still be there, but I would have to think the chances are very 
slim, unfortunately.

Now, if we were to make a new GIME in VHDL and a big FPGA, we could 
always put it back in!




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