Hi Stu: Stu Midgley wrote: > sorry, forgot to reply all... don't you hate gmail's interface sometimes? > > > What is the memory latency of the woodcrest machines? Since memory > latency really determines your memory bandwidth.
Hmmm... not for large block sequential accesses. You can prefetch these assuming enough intelligence in the code generator (heh), or the hardware if the memory access pattern is fairly consistent. Latency really defines the random access local node GUPS, well, its really more complex than that, but roughly that. That said, I would like to measure this. I have an old code which does this, any pointers on code other people would like me to run? If its not too hard (e.g. less than 15 minutes) I might do a few. > If Intel hasn't made any improvements in latency then the limited > number of out-standing loads in the x86-64 architecture will limit the > bandwidth regarless of the MB/s you throw at it. Hmmm... Ok, you are implying that if your processor can consume the load/store slots faster than it can launch them, and there are a limited number of memory operations in flight (2? as I remember, not looking at my notes now), it is going to be load-store pipeline limited, not necessarily "bandwidth". That is, the memory system would be significantly faster than the CPU can consume. I haven't looked closely at the Woodcrest arch yet. Don't know precisely what they are doing here and how it differs from AMD. Would be interesting. So far I haven't been impressed with code that I thought I should be really impressed with on this machine. Oddly the performance was about what we got out of the Core Duo on this platform. -- Joseph Landman, Ph.D Founder and CEO Scalable Informatics LLC, email: [EMAIL PROTECTED] web : http://www.scalableinformatics.com phone: +1 734 786 8423 fax : +1 734 786 8452 or +1 866 888 3112 cell : +1 734 612 4615 _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
