[mafribe]

SIMD is orthogonal to clock-speed.

There is indeed a lot to gain from having a single instruction trigger more complex behaviour, for example better instruction density, less instruction decoding needed, but all of this is independent of clock frequency.

I think, but am not sure, that the Thinking Machines' CM-2 from 1988 was a 4096 or 8192 wide SIMD machine. Surely, at the time, clockspeeds where low.