Subject: Re: CCL:Pentium vs. PowerPC speeds for quantum chemistry?

From: [email-masked] (Graham Hurst)
Date: Fri, 29 Jul 1994 17:08:33 -0400

Paul A Cahill <[email-masked]> asks:

> I'm trying to compare the capability of a 32 MB/2GB pentium system that
> costs about $5600 to a PowerPC based IBM RS/6000 that costs more than
> twice as much for the same configuration.  Given that similar codes are
> now available for both, does anyone have *real* tests of computational
> chemistry codes (speed, ease of use).  Will the PowerPC as implemented
> by IBM really provide twice the performance (both are 66 MHz).

The other results that I've seen posted seem to be for FORTRAN codes.
Here are some timings for HyperChem, written in C, for comparison.

MNDO energy and gradient for C60, converged to 1e-2, without DIIS:

Computer                  Time (s)     Rel. speed
486DX 50 MHz                375             1
Pentium 90 MHz              87.6           4.28
SGI Indy 100 Mhz            77.8           4.82
IBM RS/6000-250 66 MHz      51.8           7.24
DEC 3000 200 MHz (I think)  42.4           8.84

The first two numbers are for full HyperChem (user interface and
calculation module) running on the same processor under Windows 3.11.
The last three are for the computation module running on the unix
computer with the HyperChem user interface running on a 486.  All
times are wall clock times for start to finish observed on the PC.

Scaling by 90/66 would make the PowerPC more than twice as fast
as the Pentium, but I would strongly recommend a 90 (or 100) over a
60 or 66 for the Pentium (it's a newer, cooler, chip design).

As far as ease of use, you've certainly got a lot more OS and application
choices for the Pentium (AIX vs DOS, OS/2, NT, several UNIX choices...).

Hope this helps,

Graham
------------
Graham Hurst ([email-masked])
Hypercube Inc, 7-419 Phillip St, Waterloo, Ont, Canada N2L 3X2 (519)725-4040
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