Maho NAKATA writes: > From: Michael Poole <[email protected]> > Subject: Re: Only 70% of theoretical peak performance on FreeBSD 8/amd64, > Corei7 920 > Date: Mon, 12 Apr 2010 10:06:55 -0400 > >> Nakata-san's theoretical performance numbers assume 4 to 4.2 operations >> per core per cycle at the nominal (2.66 GHz, non-TurboBoost) clock rate. >> (DGEMM is double precision, but I am not familiar enough with scientific >> computing or with the Nehalem implementation of SSE to know why it is >> four operations per cycle rather than two -- is it because double >> precision counts as two FLOPs or is it because of multiple issue?) >> TurboBoost runs up to 2.93 GHz on this CPU, so it doesn't fit either the >> theoretical peak performance or the performance discrepancy very well. > > Hi Michael, > I read http://www.intel.com/support/processors/sb/cs-023143.htm > and TurboBoost on 920 is 2.80GHz.
Ah. I was looking at http://ark.intel.com/Product.aspx?id=37147 . Given a 2.80 GHz TurboBoost, the 44.8 GFLOPS theoretical performance number makes sense. I think the more important point is that TurboBoost on this CPU gives at most a 10% speedup, so it cannot explain the 25% performance difference. Michael _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "[email protected]"
