11 May
2019
11 May
'19
5:32 p.m.
I'm building my own 8-bit CPU from TTL chips, and
this caused me to
think: how were 32-bit minis built in the late 70s and early 80s? In
particular, how was the ALU built? I know about the 74181 4-bit ALU,
and I know (from reading A Soul of a New Machine) that PALs were also
used.
I'd be curious to know how many designs used the 74181 instead of
scratch logic in the early 70s. I doubt many custom chips were done
until mid-late 80s.
Prime used 74181 chips for some of their CPUs. I have a 150 CPU board
(1980, though it was likely a relatively minor rehash of an older
board), for example.
Prime and Data General both used AMD2901 (1975) family stuff in some of
their designs.
Prime definitely had a lot of the logic into VLSI chips on their CPU
boards in the late 80s time frame. By the end (early 90s), a CPU board
was one or two big CMOS chips and a lot of empty space.
De