[rescue] e4k / 250/1mb cache vs 250/4mb cache

Skeezics Boondoggle skeezics at q7.com
Sat Oct 9 21:43:52 CDT 2004

On Fri, 8 Oct 2004, Steven Hill wrote:

> Anyway, I have 4x250 and 2x400 running happily.

Out of curiosity, what does prtdiag -v show on your machine?

I was under the impression that until the Ultra-III-based systems came
out, mixing speeds was officially unsupported, and even if it does happen
to work, the system simply finds the least common denominator - clocks
down the faster CPUs to match the slowest ones, and ignores any larger 
caches than the smallest.

I'm almost positive that was true of, say, the sun4d and sun4m boxes; put 
an SM51 and an SM61 in a Sparc 20 and it'll run them both at 50Mhz.  Put 
some SM81's in an SC2000 with some SM81-2's, and it'll just ignore the 2nd 
meg of cache on the larger modules.

Of course, in the E10k you could set up separate domains and run sets of
matching processors at full speed, but the Ex[05]00 machines don't support

If your E4000 is *really* running mixed speeds and mixed cache sizes, then
Sun has been awfully quiet about backporting support for that from the
latest Solaris releases (that DO work as expected on US-III machines) on
the US-II Enterprise servers; but maybe those enhancements weren't
specific to the SunFire platform, but Sun just didn't make any fuss about
it because they want people to get off the older machines and upgrade...
the rare & expensive 466Mhz/8MB US-II modules are finally coming down in
price, so it'd be slick to add some of those to my E4500. :-)

-- Chris

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