This is not true. Before multi-core processors there were many computers with multiple CPUs.
Is the author under 30 or something?
It doesn't say computers could only execute one instruction at a time. It says processors.
If you're going to do needlessly pedantic bikeshedding, at least get it right.
It is not true.
Instruction-level parallelism existed before multi-core.
> If you're going to do needlessly pedantic bikeshedding, at least get it right.
Pot, meet kettle.
Then don't say shit like "at least get it right".
He's trying to describe the difference between multi-threading and multiprocessing to introduce the idea of task switching. But the bad history lesson is distracting.
There were long periods of history when most hardware vendors had at least one model with multiple processors, and there were some companies that specialized in them (Cray, Silicon Graphics, IBM, Fujitsu, Toshiba?), including ones built with x86 processors (Sequent, IBM).