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Slothie · 5th Jan 2021, 6:05 am

While the 6550 RAM is functionally equivalent to the 2114 RAM (i.e. its 1kx4) the 6550 has 4 chip select inputs (2 active low, 2 active high) and a Phi-2 clock input to synchronise the write timing so a direct pin adapter is not easy. In the case of my 2001-8 the RAM failed a few years after buying the computer (just out of warranty...!) so we took the opportunity to upgrade to a 32k dynamic ram card that plugged into the CPU socket with the CPU plugged into that. I suppose you could do that these days with a single 62256 RAM chip!

I did design a 6540 ROM -> 2716 adapter (which has 5 chip select inputs!) so its possible you could make similar adapters for 6550->2114 rams.

5th Jan 2021, 6:05 am	#7
Slothie Octode Join Date: Apr 2018 Location: Newbury, Berkshire, UK. Posts: 1,287	Re: Commodore PET 2001 While the 6550 RAM is functionally equivalent to the 2114 RAM (i.e. its 1kx4) the 6550 has 4 chip select inputs (2 active low, 2 active high) and a Phi-2 clock input to synchronise the write timing so a direct pin adapter is not easy. In the case of my 2001-8 the RAM failed a few years after buying the computer (just out of warranty...!) so we took the opportunity to upgrade to a 32k dynamic ram card that plugged into the CPU socket with the CPU plugged into that. I suppose you could do that these days with a single 62256 RAM chip! I did design a 6540 ROM -> 2716 adapter (which has 5 chip select inputs!) so its possible you could make similar adapters for 6550->2114 rams. Attached Thumbnails