Those four missing ICs seem weird, though. The other
board is is fully
populated. Were they just pulled before the PDP was trashed? Or is that
a valid configuration?
I don;t think it's a 'correct; configuration, but it can work.
Those extra ICs are more RAM chips, used to store the parity bits for
each byte. If you don't have a partiy generator/checker board in the
machine, it';ll work fine without them,