Building a PC to run Molpro

[Dave Moore]

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Hi,

The size of the SCSI drive really depends on the size of the
calculations you want to run, since it will need to write the
integral table to the disk ... of course there is the issue of the 2
GB file size limit here as well .. but I think there is now a patch
for that.  In our set up I use two 18 GB SCSI drives ... one is pure
scratch space where the calculations are run .  The other SCSI
contains the operating system and the MOLPRO executable ... I also
have it set up to store certain scratch files on the second disk to
improve I/O performance .. particularly for the sorting of the
integral table (this is a good idea ... see the manual for details on
how to set it up).  In theory, one could get even better performance
by using a software RAID array of SCSI drives to achieve even better
performance, but I have no experience with this.  One note of caution
... I tried using an IDE drive for the OS and MOLPRO executable, and
just having two SCSI's for scratch space, and I incurred a very large
performance hit ... however this may have been a configuration error
(I didn't do extensive testing).  Hope this helps,

Dave Moore


- -----Original Message-----
From: Wheeler, Dr M.D. [mailto:mdw10 at leicester.ac.uk]
Sent: Monday, July 09, 2001 10:53 AM
To: 'Dave Moore'
Subject: RE: Building a PC to run Molpro


Dear Dave,
Thanks very much for the advice, I am currently considering a newly
released
motherboard, the Tyan Thunder K7 with two AMD Athlon processors
(1.2GHz) and
1GB of RAM.  I hadn't appriciated the I/O problem, I will look into
buying a
SCSI drive, does it need a very large capacity > 10 GB ??

Once again thanks for the info,

Martyn

- ----------------------------------------------
Dr. Martyn D. Wheeler
Department of Chemistry
University of Leicester
University Road
Leicester, LE1 7RH, UK.
Tel (office): +44 (0)116 252 3985
Tel (lab):    +44 (0)116 252 2115
Fax:          +44 (0)116 252 3789
Email:        martyn.wheeler at le.ac.uk
http://www.le.ac.uk/chemistry/staff/mdw10.html

- -----Original Message-----
From: Dave Moore [mailto:dtmoore at email.unc.edu]
Sent: 09 July 2001 15:41
To: Wheeler, Dr M.D.
Cc: molpro-user at tcpc3.bham.ac.uk
Subject: RE: Building a PC to run Molpro


 
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Hello,

	Below is a summary of what I know from my own experience building
MOLPRO-tailored PC platforms.  I think it would be great if the
MOLPRO community could make available lists of hardware components
from their PC-platforms, but I don't know if is strictly ethical to
put on the MOLPRO mailing-list ... I wouldn't want the MOLPRO team to
get in legal trouble for "endorsing" specific hardware manufacturers.
 I would be happy to exchange private emails with interested parties
however. 

	1)  AMD is the better choice for number crunching in general .. this
seems to hold true for MOLPRO as well
	2)  You pretty much have to use SCSI drives (10K RPM are best) to
avoid I/O bottlenecks ... buying the memory-direct package may also
be an option, although I do not have any experience with this
	3)  There is at least one motherboard/chipset combination (ASUS 7A +
VIA Apollo 133) that cannot handle the I/O bandwidth from MOLPRO with
an Athlon/SCSI system as above ... this is an extrememly frustrating
problem when you encounter it, because MOLPRO will have
non-reproducible "numerical errors" for no apparent reason.  We are
in the process of testing another ASUS motherboard with a different
chipset, and everything seems to be fine ... a MOLPRO job that used
to crash somewhere between 1 and 16 hours has been running for over a
week now with no problems.

	Hope this helps .. feel free to ask any other questions.

Dave Moore
Chemistry Dept.
Univ. of North Carolina at Chapel Hill

- - -----Original Message-----
From: owner-molprouser at tcpc3.bham.ac.uk
[mailto:owner-molprouser at tcpc3.bham.ac.uk]On Behalf Of Wheeler, Dr
M.D.
Sent: Sunday, July 08, 2001 3:51 PM
To: 'molpro-user at tc.bham.ac.uk'
Subject: Building a PC to run Molpro


Dear Molpro Users,
I am a new Molpro user and I wish to build a PC specifically to run
calculations on.  I was wondering if anyone could offer any advice as
to
what hardware they use Pentium vs AMD and any other useful tips??

Thank you in advance,

Martyn Wheeler

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