Adding to some of these other comments, when IBM did their groundbreaking 32 bit System/360 in the 1960's, they started with a nice silicon transistor based logic family, but it pretty much ran at only one speed. So to deliver a family of computers with the same ISA, they microcoded the slower ones.
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Adding to some of these other comments, when IBM did their groundbreaking 32 bit System/360 in the 1960's, they started with a nice silicon transistor based logic family, but it pretty much ran at only one speed. So to deliver a family of computers with the same ISA, they microcoded the slower ones.
The very slowest one had 8 bit wide execution units, and presumably used similar techniques to deliver its 32 bit macroarchitecture. Per Wikipedia (https://en.wikipedia.org/wiki/IBM_System/360), the Model 30 in 1965 could execute "up to" 34,500 instructions per second, the hardwired Model 75 could do about a million. See e.g.: https://en.wikipedia.org/wiki/IBM_System/360#Table_of_System...