Author: Vincent Diepeveen
Date: 02:18:43 08/04/05
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On August 03, 2005 at 13:34:09, Robert Hyatt wrote: >On August 03, 2005 at 10:21:20, Gian-Carlo Pascutto wrote: > >>On August 03, 2005 at 10:13:45, Sedat wrote: >> >>>Hi there, >>> >>>Does anybody has any information about this processor ? >>> >>>-Can i run engine-matches with ponder on ? >>> >>>I mean: >>>-Does the kns of the engines will fall down ? >>> >>>And if its possible to run ponder on matches : >>>-is it enough just one processor or i need to buy two processors ? >> >>A single dualcore processor behaves almost exactly like a 2 processor machine. >> >>-- >>GCP > >This needs a _lot_ more testing before saying that so positively. I've been >testing on a quad dual-core box, and there are most definitely "issues" to deal >with that I/we have not yet solved. There are some memory issues that I am >working on quantifying, probably related to two cores sharing a memory bank and >the associated bus contention. First cut on the quad 875 box produced some >really ugly SMP results for me, with the NPS "scalability" only reaching 4X >generally, where on the quad 850 I last tested on, it scaled perfectly for 1-4 >processors... > >More as I work out the glitches (I hope).. This is because crafty doesn't scale. Not a hardware issue. Memory latency is 234 ns to get 8 bytes of TLB trashing memory from 250MB buffers (in total 2GB ram for total testblock). Compare with 400 ns that your own dual Xeon needs to deliver the same and compare with 700 ns that 8 processor Xeon needs. I guess the central lock structure in crafty breaks it at 8 cpu's. Diep is not central locking, of course tested to work at ugly latencies until 500 cpu's and has zero problems with quad opteron dual core 1.8Ghz at which i play at. Please note the latency for 2.2Ghz dual cores is far better because the latency of each memory controller is somewhat dependant upon the speed of the processor. So the problem is not the hardware at all, but software issues within crafty. Any default x86-64 core 2.6.10 or later by default already is NUMA and works perfectly. No need to compile your own core. I installed Ubuntu at quad, upgraded to x86-64 kernel (thanks to Mridul Muralidharan for his big help!) and it worked fine. Ubuntu is the superior distribution nowadays. Vincent
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