[SunRescue] SS1000 questions...

Martin Frost martin at dsres.com
Thu May 25 09:36:28 CDT 2000

Patrick Giagnocavo wrote:

> I have 2 system boards for my SS1000, thus have 4 MBus slots.

> 2 of those slots are filled with either 40 or 50Mhz CPUs.  Both are on the
> first system board.

> If I get two more CPUs to fit on the second board, do they have to
> be the same speed, or can they be different speeds from the CPUs on
> the first board (like SM81's which run at 85Mhz)?

There are two separate issues. Firstly, different CPU revisions need
slightly different initialisation by the boot ROM, so certain
combinations won't work at all.

Secondly, the OS scheduler assumes all CPUs are the same speed. If
they aren't, then scheduling will be non-optimal and some processes
may suffer starvation.

Both of these mean that mixing different CPUs is a Bad Thing.

I should acknowledge that I didn't know either of these things until
James Lockwood posted about them a month or so ago. ;)


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