[SunRescue] SS20 (??) is it really?

James Lockwood lockwood at ISI.EDU
Fri Jul 30 14:09:30 CDT 1999

On Fri, 30 Jul 1999, j. grubman wrote:

> If it helps any, I'm running an SS20MP w/ one 150 MHz and one 133 MHz RT626
> Hypersparc. Both processors have 512k of external cache. The system runs fine
> under Solaris 2.6 and 7. A friend at Sun tells me that, while it's entirely
> unsupported, mixing different models of the came CPU shouldn't cause problems.

This depends on what you consider the "same CPU".  My original post was an

Nearly any HyperSPARCs will work with each other, though stick with
modules with the same cache size for safety.

SuperSPARC-I (SM41/51/61) and SuperSPARC-II (SM71/81) should not be mixed.

Mixing SM51's and SM61's in a SS20 is a waste as your mbus clock will slow
to 40MHz.

Mixing SM71's and SM81's is kind of silly as the speed increase is not
dramatic and you would do better by selling the SM81 and buying another

Mixing SM41/51/61's in a SS10 is silly as they are slow and you can get
better performance cheaply.

The only SuperSPARC CPU mix that I might try would be an SM52X with an
SM51 in a SS10 or SS600, giving a 3-processor system.  This works 100%
with no problems.

In general, mixing CPU's is a bad idea because the slower CPU will become
a bottleneck under load (much like mixing fast and slow disks in a RAID 0
stripe).  With SM61's and SM71's falling in price so much, it seems like
they are the way to go.


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