[SunRescue] MBus CPU's in a SC2000

[Björn Ramqvist]

Mike Nicewonger wrote:
> 
> > I think it's all BS.  I don't have the part numbers with me, but
> > I put an SM61-2 in my 4/600 board and it ran great.  SM61-2 is
> > listed as not being supported in the 4/600,SS10 and SS20.  I have
> >  no idea if it is using all 2MB or not, but it runs very well.
> 
> The SM-61-2 will work in any of the M-bus machines. They just will not be
> able to address the second MB of cache memory. This is also true for the
> SM-81-2 so long as your PROM supports the SM-81. Althought this is not a
> 'supported' configuration it does indeed work just fine.

Exactly.
All SMxx (I think) are Mbus-capable and just some of'em are
Xbus-capable. Yes, Xbus. Looks just like a Mbus-slot, but is
packet-switched instead of circuit-switched. All SS1000(E) and SC2000(E)
along with the Cray CS6400 use this protocol, and is interconnected (or
distributed?) through the XDbus, the backplane interconnect.
The SM61-2 and SM81-2 has 2MB cache onboard, but as you say, only the
SC2000 is capable of using the 2nd MB of cache. Both of these modules
are Mbus-compatible and are indeed functional as regular Mbus-modules.

Hope this clear things up for the SS1000(E) owners also. =)

/Bjorn