Re: NetBSD/vax vm for github testing

[Mouse <mouse%Rodents-Montreal.ORG@localhost>]

> Also, emulating multiprocessor support in general using a
> multiprocessor machine is extremely difficult, since you need to
> synchronise the CPUs so that they emulate at exactly the same speed.

Why?

I'm reasonably sure this isn't true for values of "in general"
including non-VAX machines, as (for exmaple) SPARC-20s can have
processors with wildly different clock speeds.

As for VAXen, what is there that requires the two processors to be
running at exactly the same speed?  In the one case I know enough about
to be confident of - the MicroVAX-II - I'm fairly sure it's not true of
real iron; different processor boards have independent clock
oscillators, which can never be _exactly_ the same speed, even if they
are running at the same nominal frequency.

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