[Coco] CoCo 1 64K upgrade failed :(.

[Phill Harvey-Smith]

Mike Pepe wrote:
> Phill Harvey-Smith wrote:
>> Nope, not acording to the data sheets I have and :-
>>
>> http://www.cbmhardware.de/mosic/ram4108.php
>>
>> That's IIRc what some of the jumpers do, re-route the voltages.
> 
> That's good to know. I'll be careful if I do the upgrade then. I 
> remember seeing some home-upgraded D boards that bent the pins out of 
> the sockets and had them connected via flying leads- probably because 
> the jumpers weren't appropriate for 4164's at all.

Indeed, it was the other way around with the Dragon, the early boards 
had jumpers that let you select the voltages/signals between 1 or 2 
banks of 16K, or 64K, the 32K machine IIRC was origninaly intended to be 
16K, but when Sinclair relased the 48K spectrum it was upped to 32K, 
which could either be 2 banks of 16K, with the second bank on a patch 
board, or a bank of half good 64K.

For some strange reason later versions of the board didn't have the 
jumpers and where laid out for 2 banks of 16K all on the main board, I 
have upgraded a couple of these in my time (including my original 
machine), and it's defo a cut and re-route job :)

Cheers.

Phill.

-- 
Phill Harvey-Smith, Programmer, Hardware hacker, and general eccentric !

"You can twist perceptions, but reality won't budge" -- Rush.