> 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
