[Coco] [Color Computer] Sam/Ram question.

Phill Harvey-Smith dragon at aurigae.demon.co.uk
Wed Dec 28 06:47:11 EST 2005

Hi there,

I mentioned a while back that I was working on getting the SAM in the 
CoCo 1/2/Dragon to talk to static RAM, I think I have this mostly 
working, currently implemented with a pair of LS latches and an Atmel 
16V8 PLD. I still think this requires a little work as it does have a 
couple of problems, however I can boot into basic and everything seems 
to work ok. Asuming I can get this working correctly, the next stage 
would be to graft on some sort of bank mapping to allow >64K memory.

However the most serious problem I am currently having is that it seems 
to stop working after about 10-15 minutes, I suspect something is 
getting too hot, though nothing appears to be getting hotter than with 
normal DRAM connected.

One thing I did wonder about is that the original CoCo/Dragon circuit 
sheets include a bank of 33 ohm resistors between the SAM and the RAM 
address lines, I have not included them, in my circuit could this be the 
cause of the problems, I could never work out just what they where there 
for anyway :)



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