I checked the 1977 IC Master, and the uA3656 is not listed. It does say
that the uA prefix is the Fairchild linear series. In going through the
Fairchild catalogs, I too have been unable to find any references, and
am now curious if the number is correct.
I have a catalog from 1969 which lists their MOS parts
in the 3xxx
range.
They didn't make RAM in 1969, will try to dig out an
early 70s catalog to try to find 3656's (I'm guessing they will be in
the '72 or '73 ones).