From schuetz@iacrs2.unibe.ch  Thu Mar 18 09:35:18 1993
From: schuetz@iacrs2.unibe.ch (Martin Schuetz)
Message-Id: <9303180735.AA17769@iacrs2.unibe.ch>
Subject: Re: Information about IBM RS6000
To: ZSHI@ac.dal.ca (Zheng Shi)
Date: Thu, 18 Mar 1993 08:35:18 +0100 (NFT)


> 
> We are planning to buy two IBM RS6000 computers, one at top level (580) and the
> other lower to middle model. We will run ab initio packages most of the
> time. We would like to hear your advice about the system configuration, i.e.
> memory size, disk space and disk controllers.  Also, information about 
> workstations from other vendors would be most helpful.
> 
> Thanks in advance.
> 
> Zheng Shi
> 

We have three IBM RS6000 computers in our lab for ab initio calculations, two
350 systems and one 320E system. Each machine has 64MB main memory. In order to save disk space the machines are configured as /usr server/clients in a NIS
(YP) environment. Each machine has its own scratch disk of 1-1.6 GByte. We 
usually run Gaussian 92 on these machines. Since the RS6000 is faster in 
SCF=direct mode, 1-1.6 GByte scratch disk space suffices for most applications.
For larger calculations (analytic 2nd derivatives at the HF level (CPHF) with
250-300 basis functions) the 64 MB seem to be a lower limit for the main 
memory. In order to prevent the large ab initio jobs from disturbing inter-
active jobs we have patched the public domain version of NQS in a way that the
jobs on the NQS queues are running at a fixed low priority, and not in the
UNIX niceness scheme. The patched NQS version can be obtained by anonymous ftp
from one of our sites (iacrs2.unibe.ch, /pub/aix/nqs.tar.Z).

Hope that helps


- 
Martin Schuetz                              Phone: +41 31 65 42 40
Institute for Physical Chemistry            FAX:   +41 31 65 44 99
University of Berne
Switzerland                                 schuetz@iacrs2.unibe.ch