CPU card
In principle, this is the ALU with the register file. Except for two black 28
pin ICs (64x9 bit TTL RAM) at the middle top, everything is IBM custom. And
also for the other DIL TTL ICs you need a list in order to decipher what
function they contain. That's because - of course - IBM also labelled
standard ICs from other manufacturers with a proprietary number.