ATHLON vs XEON: number crunching

[Ivan Oleynik]

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


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Ivan I. Oleynik                       E-mail : oleynik at chuma.cas.usf.edu
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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