Re: NetBSD/vax vm for github testing

> I wrote multiprocessor support for NetBSD/vax many years ago; but not many vax machines can
> have multiple CPUs. It did work on VAX8250, which was just over one VUPS (which is extremely
> slow today). 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. -- Ragge

Just curious: why would multiple CPUs need to emulate at exactly the same 
speed? I've read about multiprocessor VAXen running different CPUs, and 
I've run different CPUs on other architectures (Celery and Pentium II with 
i386, SPARC and HyperSPARC on, well, sparc).

Were the people running different CPUs in a VAX doing something different?

BTW - someone modified SIMH to run multiple CPUs, but only supported 
OpenVMS. The author had no interest in NetBSD.

https://oboguev.net/vax_mp/

John