Subject: Re: CCL:Question regarding Mac G5 performance

From: Mike McCallum <mmccallum(at)pacific.edu>
Date: Wed, 19 May 2004 10:49:14 -0700

On May 19, 2004, at 05:06, Joe M Leonard wrote:

> Folks, has anybody run QM or MD benchmarks on a dual-processor
> 2GHz G5 that they care to share?  I'm particularly interested
> in how they stack up to the newest/newer Opteron and Pentium4
> machines.  If you've worked with the newer Mac's, (a) is it
> possible to get good, useful 2x processor performance for
> double-precision code?  (b) what compilers are required to get
> (a)?  (c) is Altivec useful for double-precision code, or
> merely for int/float work?
>

I had done some comparisons between price/performance, and I found dual  
G5s to be at or near the best in price/performance, especially if  
things are recompiled with the IBM compilers (between 8-10 % speed  
increase over pre-compiled (with apple gcc) versions of NAMD2, and  
using standard gcc for charmm).  I would expect that things like  
gaussian03 run very well (I believe gaussian uses the IBM compilers for  
macOS).  For MD, the speedup seems to be due to the on-chip square root  
eval.

The built-in Gigabit enet is attractive, also, as charmm and NAMD scale  
very well with gigabit, and it makes myrinet less price-effective (when  
used on any platform, wintel included, see
http://biobos.nih.gov/apps/charmm/charmmdoc/Bench/c30b1.html for  
example).  I decided that dual G5 xserve cluster nodes with gigabit  
switches were much more cost-effective for me than any other processor,  
especially any high-bandwidth specialty comm method (apple's gigabit  
has a pretty low latency also).

Additional considerations for us were the BSD environment which is more  
secure than windows, and the OS is arguably more stable and supported  
than a linux (though you can pretend to be linux with the fink layer).   
Being much more familiar and happy with OS X than windows or linux  
sealed it.

It is my impression that opterons, PIVs, G5s all have their advantages,  
and disadvantages, so your own comfort level may be a non-trivial  
consideration.  I don't feel there is any net performance penalty, and  
often a benefit from using G5s.

> A quick glance at apple.com suggests these machines go for about
> $3200 USD, which isn't that different from numbers gained from a
> quick glance at dell.com.  I know IBM chips were number-crunchers
> in the good old days, and I assume that's still the case now (which
> is why I'm looking to CCL for guidance :-).

I got my current dual 2.0 G5 for $2200.  This is acadmic pricing, and  
I'm sure your rep would give you a similar price, especially now that a  
new processor version is close to (?) production.  I was looking at at  
least $2500 for a similarly configured opteron node (w/o gigabit,  
though).

Hope this helps,

Mike
>
> Thanks in advance!
>
> Joe Leonard
> jle(at)theworld.com
>
>
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--
C. Michael McCallum                         
http://chem.cop.uop.edu/cmmccallum.html
Associate Professor
Department of Chemistry, UOP
mmccallum .at. pacific .dot. edu                (209) 946-2636 v  /  
(209) 946-2607 fax