[Coco] 64 K upgrade for COCO 1 gives ?OM ERROR
Bruce W. Calkins
brucewcalkins at charter.net
Sat May 2 21:09:44 EDT 2020
On 5/2/20 7:44 PM, John E. Malmberg wrote:
> On 5/2/2020 5:26 PM, Bruce W. Calkins wrote:
> > "E" and earlier boards needed some added wiring to a previously unused
>> gate on a 74LS02 to properly switch the RAM. Only the "285"/"F"
>> boards were a direct upgrade.
> It is definitely an E board.
> So I may need more information on how to upgrade this computer to use
> the full 64K.
I upgraded my "E" board back in "the day." A little wire-wrapping and
lifting a pin or two on the 74LS02. It was my first CoCo upgrade and I
still remember how my heart was beating with fear that I might kill my
computer. I still have that machine, although it wears a J&R Banker
256k upgrade now. I know I still have the instructions for that
original 64k upgrade too, but just where in the midden heap is the question.
More information about the Coco