[Coco] Any info on a mystery 256 color GIME mode?

[Nickolas Marentes]

John Kowalski and I have both clobbered all the know registers with random
data and while some strange effects were seen, none activated the mystery
256 color mode.

I was wondering if anyone has any idea what the the TEST pin (39) does on
the GIME chip. It is marked as TEST in the Tandy CoCo3 service manual but
other memory maps I've seen mark it as Z5.

While I'm riding 50/50 on believing this 256 color mode exists, I do believe
that at some stage on at least a very early version of the GIME, 256 color
mode did exist else the information in the Tandy R&D manual would not
mention it.

I believe we need to find people who were closely involved with the GIME
design during the early stages of development.

Regarding an FPGA clone of the GIME, I am wondering if there is anything
that can be done outside of the GIME to enhance it, similar to the way 2MB
RAM has been added. Is there any "tricks" that can be done to add features
or boost performance such as giving the 6809 it's own bank of RAM seperate
from the GIME's RAM and possibly swapping the banks?

Nickolas Marentes