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> That's insane. What's even more insane is that a bit over 20 years later homecomputers reached that frequency. And in the next decade they reached over 100 MHz.

The CDCs still had a good run. This line was originally released in 1964. It started at 10MHz, but that was 60 bit words, and special floating-point systems. IIRC floating-point multiplies were only one clock cycle; if that's correct, it took 100 nanoseconds.

The Apple II came out in 1977, 1MHz, 8 bit CPU and no floating-point circuits. You had to use many cycles to do any floating point, and typically you only used 32-bit floating point (because it was painful enough there). A single 32-bit floating point multiply took 3-4 milliseconds according to: https://books.google.com/books?id=xJnfBwAAQBAJ&pg=PA26&lpg=P...

The original IBM PC came out in 1981. Its clock was 4.77 MHz. But again, that was misleading. Internally the 8086 was a 16-bit CPU but its memory I/O was only 8 bits wide. It didn't normally come with a floating-point processor. There was one, the 8087, and I think the original IBM PC had a socket for it, but it cost big $$$ and the 8087 wasn't actually available for purchase until ~6 months after the PC's release. That one could go 4-10MHz. If you bought a coprocessor, you were finally getting to somewhat similar speeds for numerical calculations... but that was 16+ years later.




> Internally the 8086 was a 16-bit CPU but its memory I/O was only 8 bits wide.

Did you mean 8088 here?


Yes, 8088. Thanks for the fix. The 8088 was a 16-bit CPU with an 8-bit bus. The 8086 was a 16-bit CPU with an actual 16-bit bus.


Interestingly, the original "sx" designation for Intel 386 chips (80386sx) meant the same sort of thing... the 386sx was a 32 bit chip with a 16 bit bus. The dx was 32/32.

A product generation later, Intel changed what this meant to indicate whether or not the CPU had an on-chip FPU.


> If you bought a coprocessor,

Those were the days you looked at the TRW multipliers (packed in 64+ pin DIPs) advertised in trade magazines like auto buffs might at V8 engines ...

Intel sold their own 8087, until it was digested into the vast expanses of CPU chips opened by scaling.




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