On Sat, 7 Nov 1998, Erik E. Fair wrote:
> I've got a copy of the Sun FE's manuals here, and in my reading of
> them, I don't think you can put two (or more) CPUs of different clock
> rates on the same Mbus; the Mbus clock is taken as a division of the
> CPU clock, with a maximum of 40 or 50 MHz, and two different CPU
> clocks are going to result in incompatible Mbus clocks...

Sun doesn't officially support such configurations but I know people who
have run 2 different MBUS modules of the same CPU type (SuperSparc,
HyperSparc). 

The magic is in the cache controller on the CPU which is the only bit that
is clocked at the MBUS speed.  The CPU is driven from a clock multiplier
off the MBUS clock.

So a SM51 and an SM61 would work just fine in a SS20.  Both would run at
50mhz MBUS speed but the SM61 would run at ~60mhz while the 50 ran at
~50mhz. 

-- 
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