From chemistry-request -A_T- ccl.net Mon Mar 25 15:41:53 1991
Date: Mon, 25 Mar 91 15:07:11 EST
From: m10!frisch-: at :-uunet.UU.NET (Michael Frisch)
Subject: Gaussian 90 SCF times
To: chemistry#* at *#ccl.net
Status: R

    
On the subject of workstations for ab initio calculations, one person
commented:

    We have been having very good experience with the Silicon Graphics
    RISC servers, running both Gaussian-90 and GAMESS (as well as a
    host of other numerical simulation, scattering theory, and other
    heavy computations).  Running on one (of the 4) CPU of a year-old
    4D/340 with 33Mhz CPU's, a large (ca. 850 Mb of scratch) SCF
    (G-90) calculation which took 100 minutes on a CRAY-XMP, ran in
    only 300 minutes on our SGI box.  I understand that < $20K 1-CPU
    versions of this machine WITH graphics are now available, and from
    our experience, they would also be very robust multi-user servers;
    we are usually running with several background jobs, plus several
    interactive users using both dumb terminals and X-terminals, and
    notice no real problems.  These machines can also be readily
    goosed up with cheap memory (e.g., $982.Cdn/8Mb from Kingston) and
    SCSI disks (ca. $3300.Cdn/1.2Gb) from 3-rd parties.
    
    
    
The SGI is a good machine, however, I'd like to point out that an SCF
job which takes 100 minutes on a Cray in Gaussian 90 using
conventional SCF typically takes half that much CPU time when run in
direct mode.  That doesn't change the above conclusions, but we would
like people to get the most out of their Crays as well!

Michael Frisch
Gaussian, Inc.

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