Re: CCL:Opteron or Nocona ?

 Actually, highly optimizing compilers for Opteron do exist (such as
 Pathscale). Even Intel Fortran 8.1 (either 32 or 64 bits) produces
 decent code for Opteron since Opteron is not as fragile as Pentium 4 in
 terms of which code it likes and which it does not.
  There is  one specific situation where Nocona could come as a clear
 winner, but such cases are not too common. Basically, codes that run
 BLAS routines such as DGEMM for the majority of their runtime gain a
 lot on Nocona when the correct libraries are used. This is because both
 Opteron and Nocona run BLAS proportionally to the clock speed, so the
 much higher clocked Nocona wins (~3 vs ~2 Ghz). On the other hand,
 multi-processor Noconas can choke because of limited memory bandwidth,
 whereas Opterons under such circumstances do just fine.
  Last, here are some last year's Gaussian03 benchmarks, where both
 Opterons and Noconas were comparable:
 http://www.princeton.edu/~kkudin/g03_b5_tests_1.txt
  YMMV ...
  Kostya
 --- mark somers <m.somers * chem.leidenuniv.nl> wrote:
 > Dear Luigi Cavallo,
 >
 > we have recently purchased and setup a new Beowulf cluster here in
 > Leiden,
 > dedicated to run ADF and other DFT codes (Dacapo and Vasp) on it. We
 > have
 > found the Nocona's, in combination with the Intel compilers, to be
 > the best
 > combination especially for ADF and ADF-BAND.
 >
 > Before we decided to go for the Nocona's, we did try with two test
 > machines,
 > one being a dual-cpu AMD Opteron 246 (2.0 GHz) and the other being a
 > dual-cpu
 > Nocona (3.0 GHz). Tests showed that the AMD has, in general, a
 > slightly
 > better cache hierarchy and a better memory scalability, but also that
 > the
 > lack of compilers able to tune for the Opterons is severe. Of course
 > we took
 > the differences in cpu clocks into account.
 >
 > As it turns out, after having contacted the SCM people in Amsterdam,
 > ADF can
 > effectively use the SSE3 registers and cpu intruction set and that
 > makes it
 > run fast on the Nocona's. This, together with the prices being
 > roughly the
 > same, made us decide to go for the Nocona's.
 >
 > BTW, maybe this is known to you already, but Intel offers you their
 > OpenMP
 > capable compilers for free for academic use.
 >
 > The machine is up and running now in 64 bit mode and doing fine ;-).
 >
 > Maybe the information can help you in your decision.
 >
 > Best regards,
 >
 > Mark Somers.
 >
 > > Hi,
 > >
 > > we are going to invest some money for a few computers, and we have
 > to
 > > make a decision between the AMD-Opterons and the Intel-Nocona.
 > What's
 > > better ? We are experienced with the Opterons, but we have no idea
 > about
 > > the Noconas...
 > >
 > > Major codes to run on them will be classical QM packages as ADF,
 > G03, TM,
 > > some AIMD as CPMD, and possibly some classical MD as gromacs.
 > >
 > > Thanks,
 > > Luigi
 >
 > --
 > Dr. M. F. Somers
 > Theoretical Chemistry - Leiden Institute of Chemistry  - Leiden
 > University
 > Einsteinweg 55, P.B. 9502, 2300 RA Leiden, The Netherlands
 > tel: +31715274437
 > mail: m.somers * chem.leidenuniv.nl
 > web:  http://rulgla.leidenuniv.nl/Researchers/Somers.htm
 > room: HB322
 >
 >
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