said by n1581j :
Actually, it was 256k, I happened to be there. It's the reason the original PC from IBM only provided 256K max on it's motherboard. It was only when AST and others with their Advantage, Rampage 384K boards plus ports took it to 640K, did it change. Of course you weren't old enough to know back then.
Wrong about the original PC memory restriction.
The reason IBM only put 256K on-board was:
a) the original PC was an experiment as far as IBM was concerned. They only expected to sell about 10,000 of them over its lifespan.
b) IBM had other machines in their line (not PC's per se but running an IBM proprietary os) at the time which were roughly comparable speedwise but had more memory. These machines cost a lot more than a PC (ie. 4-5x more IIRC).
c) IBM didn't want a 'capable' PC cannibalizing the sales of it's more expensive machines.