ATHLON vs XEON: number crunching

Joe Griffin joe.griffin at
Wed Jun 19 14:08:24 PDT 2002


Is your test memory limited?

Perhaps it is not the CPU speed but the cache size
that is limiting you.  The Xeon has a different
cache size and Memory type.  P4's use RDRAM (high latency/
high bandwidth).  The AMD may use SDRAM (low latency/low bandwidth).


Ivan Oleynik wrote:
> A week ago I posted a question asking people about their experiences with
> both Athlon's and Xeon's in terms of their performances in number
> crunching.
> Now I made my own tests and found very bizarre results. I only compared
> serial performance by running my representative code on each platform. The
> code was compiled with PGI compiler, no optimization options (by default
> it is -O1, local optimization), I used flags -tp athlon and -tp piv (xeon)
> for platform specific compilations.
> The code itself contains a lot of FFTs, vector & matrix algebra, it
> includes BLAS and LAPACK sources and minimal IO. All the systems have 2 GB
> RAM and the code consumes only 50 Mb.
> What I found is that Xeon 2.2 GHz is 1.5 times faster! than any athlons I
> tested. But the most strange thing is all these athlons: MP 1200, MP 1900,
> MP 2100 give approximately the same timing within 5%. This is completely
> above my comprehension.
> Did someone encounter such a strange pattern and what can be a source of
> this behavior?
> Ivan
> ------------------------------------------------------------------------
> Ivan I. Oleynik                       E-mail : oleynik at
> Department of Physics
> University of South Florida
> 4202 East Fowler Avenue                  Tel : (813) 974-8186
> Tampa, Florida 33620-5700                Fax : (813) 974-5813
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