[Coco] original 16k CoCo 1 upgrade to 64k

[Benoit Bleau]

My first coco was a 32k model, D board, and I remember vaguely that, to
unlock the full 64 K, I had to add an extra AND gate.  I think there were
also some resistors to cut, or add, not sure which.

IIRC, the F board had all the required components, you just needed to change
jumpers.  The earliest board I have ever seen was the C board, and could not
be upgraded. It required too extensive modifications.

I'm not sure how the boards are identified either. I just recall that in
84-85, I new the difference by looking at the board :(

The D board 64k mod was published in the Color Computer News magazine by
Frank Hogg to allow full ram access for Flex. I think I still have the
magazine somewhere.  Let me know if you want a scan of the article, I'll dig
it out of storage.

As for the F board, I'm sure that there's an article in Rainbow on how to
upgrade it (maybe from Marty Goodman...)


-Ben