> The Intel's SMP design is poor compared to its competitors (not just > the MoBo, the CPUs as well), that is a well known fact, but I > wouldn't be so sure that it is what hits you. Can you try to run some > some big BLAS operations like for example:
> set.seed(1) > a<-matrix(rnorm(4000000),2000) > b<-matrix(rnorm(4000000),2000) system.time(for (i in 1:20) a%*%b) > This takes ca 14.2s on a 2.66 quad Mac Pro (46.5s user time). I > wonder what the 8-core does with this. If you can't feed all 8 cores > then I'd say it's likely a bandwidth issue ... > Cheers, > S Simon, the BLAS operation above completes in 9.0 seconds on the 3.0 8-core Mac Pro. About 37% faster than you 2.66 quad, which closely matches the performance gain barefeats.com found in a recent multi-tasking test. On this test, the cores maxed out at about 70%. The remaining 30% probably gets wasted due to the I/O issue. See: April 19th, 2007 -- MULTI-PROCESSING: 8 Core versus 4 Core Mac Pro (or "What happens when four CPU hungry apps fight for all available cores?") http://www.barefeats.com/octopro3.html Best, David _______________________________________________ R-SIG-Mac mailing list [email protected] https://stat.ethz.ch/mailman/listinfo/r-sig-mac
