On Monday, March 24, 2003, at 06:36 PM, Paul Vixie wrote:
>>    But wait...why would this have anything to do with Qbus (and its 
>> 22bit
>> address space) at all?  Wouldn't such 
>> other-processors-accessing-my-memory
>> transactions happen over the PMI bus?
>
> in the KA630 (and KA65* series), the PMMI can only have one processor.
> so a multiprocessor KA630 would be several CPU's each with their own
> PMMI and its own RAM boards.  moving data from a CPU to some other 
> CPU's
> memory would go over the QBUS, using a very UNIBUS-map kind of mapping
> scheme.  this is not very different from how the 782 worked.  if you
> wanted direct access to all memory then the total memory in the system
> would have to be 4MB or less.  far better to do specific page sharing
> for DMA-like access, and let your total memory be the total of all 
> that's
> addressable by all PMMI's.  as der mouse said, this isn't traditional 
> SMP
> but it's not completely antithetical to traditional SMP either.

   Ahhhh, I get it.  Thanks for the clarification, Paul.

   I wonder what the practical limitation would be on the number of 
KA630s in such a system.    I've been doing a lot of assembler lately, 
and I have a large number of KA630s and I'm having very sick thoughts. 
:)

        -Dave

--
Dave McGuire             "I've grown hair again, just
St. Petersburg, FL           for the occasion."       -Doc Shipley