Subject: Athlon vs Intel performance

From: "M. Nicklaus" <[email-masked]>
Date: Fri, 31 Mar 2000 18:43:28 -0500

This is a follow-up to my previous posting of Wed, 29 Mar 2000:

> We've run one single direct speed comparison (I wouldn't call it a
> benchmark) so far, running the same Titan calculation on both a 600 MHz
> Pentium III (non-Coppermine) and an 800 MHz AMD K7 (Athlon) system, both
> running under Windows 98.  (The job was a single point energy calculation at
> the LMP2/6-31G** level for a nucleoside analog.)
>
> Time for completion (as per program output, but in agreement with wall time):
>
> 600 MHz Pentium III  -  7:05 h
> 800 MHz Athlon       -  2:25 h
>
> Correcting (linearly) for the difference in clock rate, the Athlon is still
> faster (for this job!) by a factor of 2.2.
>
> Specs:
>
> 600 MHz Pentium III  -  100 MHz FSB, 512 MB PC100 RAM, 27 GB ATA/66 7,200rpm HD
> 800 MHz Athlon       -  100 MHz FSB, 256 MB PC100 RAM, 27 GB ATA/66 7,200rpm HD
>
> However, we've had quite a few stability problems with the Athlon system so far
> (both in Titan and in general), but we think these are more likely related to
> hardware driver problems in Windows 98 than to true hardware instability. All in
> all, YMMV.

After cleaning up some of the Win.98 driver issues on the 800 MHz Athlon
machine, I re-ran the LMP2 single-point job.  With some substantial hard drive
slowdowns removed, the job ran quite a bit faster (see below).

Following the post of Matthias Mann <[email-masked]>
on Wed, 29 Mar 2000:
> I have only comparisions of PII-450, PIII-500 and AMD Athlon 550.
> Look at:
>       http://www.chm.tu-dresden.de/edv/bench/bench9.html
> for GAMESS(US) benchmarks, and at:
>       http://www.chm.tu-dresden.de/edv/bench/bench10.html
> for GAUSSIAN98 A7 benchmarks.
>
> Normally the relation of relative performance looks as expected;
> however, in some cases the Pentium-III system is extremly slow:
> this is the case in MP2 and QCISD(T) calculations with Gaussian
> and in CASSCF calculations with Gamess.
> I'm not sure about the reason, maybe this is the cache, or the
> architecture specific optimization (the code was compiled in both
> cases with pgf77 on an PII system, and in the Gaussian case
> maybe the optimized BLAS plays a role).
I ran an HF single-point job on the same molecule.  In keeping with the
GAMESS(US) and GAUSSIAN98 results, the extreme slowdown of the Pentium III as
observed for the LMP2 job did not occur for the HF calculation.

                        LMP2      HF

600 MHz Pentium III  -  7:05 h   24:11 min
800 MHz Athlon       -  1:44 h   16:51 min

ratio P III / K7        3.057    1.076
(clock rate-adjusted)

So this seems to be a case not of "your mileage may vary" but of "your mileage
DOES vary strongly"...

As far as I can determine (from WinTop and System Monitor), these jobs all
appear to be mostly CPU-bound and not I/O-bound, taking up 99+ % CPU cycles most
of the time with only intermittent disk writes/reads.  (The Athlon hard drive
had previously been too slow by a factor of 5.)  All other possible parameters
that people asked about, such as Titan version, Windows virtual memory setup,
hard drive access times etc. are as similar/identical as I can make/determine
them to be.  The instabilities that we have with the Athlon system are,
unfortunately, not yet completely removed.

Since I don't have access to the Titan source code, I can't say anything about
compilation etc.  Maybe Schroedinger can comment?

Marc

------------------------------------------------------------------------
 Marc C. Nicklaus                        National Institutes of Health
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      http://rex.nci.nih.gov/RESEARCH/basic/medchem/mcnbio.htm
    Laboratory of Medicinal Chemistry, National Cancer Institute
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