Another round of speculative-execution vulnerabilities

> The problem with CPU speed is we have now hit what I'll call the "Cray Limit". Cray Supercomputers were always relatively small, because the bigger the computer the longer it took the various components to talk to each other.

Cray's were about the same size as other mainframe sized computers of the days. Going much bigger wasn't really useful, because neither software nor hardware at the time was ready for massive parallelism. Today it is, and thus we have warehouse sized supercomputers that can run (some, obviously not all) HPC style problems utilizing all that parallelism.

> At roughly 1ft/ns, this means your typical ATX mobo cannot operate faster than 500MHz. Knock a nought off that, to give a 3cm chip, and you've stuck a nought on your chip speed, 5GHz. Careful placement of components will nudge that speed up, but if components need to communicate "across chip", you're stuffed ...

That matters insofar as you require everything to be synchronous, with a signal traversing from across a wire within one clock cycle. The existence of CPU cores within your CPU running at different frequencies, not to mention long distance high speed network transmission, suggests that it's possible to design things without such synchronicity requirements.