How were 32-bit minis built in the 70s/80?

Dennis Boone drb at
Sat May 11 19:32:36 CDT 2019

 > 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.


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