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Subject: Re: Call me now...

Author: Slater Wold

Date: 18:27:10 08/07/03

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On August 07, 2003 at 12:26:12, Matthew Hull wrote:

>On August 06, 2003 at 17:30:24, Slater Wold wrote:
>
>>I clicked the "Call me now" option, entered my name & number, and 20 seconds
>>later someone from IBM called me.
>
>Cool.
>
>>
>>Of course she couldn't answer my question, but I did get an answer:
>>
>>"For high performance computing (HPC) customers, the p690 has an HPC option that
>>can provide increased memory & I/O bandwidth per processor, resulting in
>>improved performance and enhanced throughput.  This specially configured version
>>can elevate performance on certain applications by as much as 30% to 45% over
>>what standard p690 configurations can provide."
>>
>>"In the standard p690 each POWER4 chip contains two processing cores that share
>>an L2 cache.  With the p690 HPC option, each chip contains only one processing
>>core, making the chip's full I/O and memory bandwidth available to the single
>>processor."
>>
>>It's about $4M, in a 32-way configuration.
>
>I still wonder though.  The PDF you pointed to only talked about SMP
>interleaving within the MCM.  It gave no indication if inter-MCM memory
>interleaving leaving once again the impression of NUMA.  Also, if the CHIP is
>reduced to one processor core in the HPC configuration, how does that affect the
>number of CPUs per MCM and does it necessarily improve NUMA latencies?  Maybe it
>only improves MCM performance.
>
>MH

In it's 'standard' config, it is a NUMA machine.

http://researchweb.watson.ibm.com/journal/rd/461/tendler.pdf

Search for 'System Balance'.  "The multi-MCM configuration provides a worst-case
memory access latency of slightly greater than 10% more than the best-case
memory access latency maintaining the flat memory model, simplifying
programming."

But the HPC option seems to end that latency, with full memory bandwidth over
the MCMs & CPUs.  But I am still getting clarification on this.



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