30$12$f3i99le@pir.net (Peter Radcliffe) writes:

>Kralizec Craig <cd@lios.apana.org.au> probably said:
>>You should never, ever combine CPU modules of different
>>speed/type. If you can, obtain another 50 or 60 MHz module and use
>>them in matched pairs of the same speed/type.

>While this is what sun will tell you ("Mixing different CPU modules is
>not supported") in practice you can mix CPU speeds in SS10s and SS20s.

>MBUS modules will coexist at different speeds as long as the MBUS
>speed is the same between the two modules, if the modules don't have
>cache this means they run at the same CPU speed, if they do have cache
>(SMx1 modules) then the bus speed is independant of the processor
>speed and they can be mixed if the bus speed is the same.

Now you've said this I do remember reading about it somewhere else in the
past. 8-) It's true that there can be scheduling problems with CPU's of
different master clock rates, but if the Mbus speed of each processor is
matched they will work together electrically on the same system board.

>The only real negative aspect of doing this is that Solaris assumes
>all processors are equal for purposes of scheduling, so CPU scheduling
>priorities may be slightly sub-optimal.

Perhaps there is a way to tweak the way each CPU is indexed for scheduling
purposes but it would not be a very good idea to be fiddling with timing
factors in software as the complexity of the kernel code would no doubt
increase significantly.

Craig.
--
Guru Will Sellit! ** 'sunrk' on Ebay ** | Get Back on Track at the Sun Shack
Craig Dewick - aka the one4sun! | www.sunshack.org or www.sunshack.net
Main info website at www.one4sun.org +-------------------------------------
SRK's Ebay Shop is now available at www.ebayshops.com.au/sunripenedkernels