[gmx-users] Opteron-Bug

David spoel at xray.bmc.uu.se
Fri Mar 19 21:37:00 CET 2004

On Thu, 2004-03-18 at 18:49, Thomas Veith wrote:
> Hi folks,
> Here we are going to get a cluster which is budgeted for approx. Euro 150.000,--.
> To get most bang for our bucks, we thought of going the AMD-Opteron/AMD64 way; but recently I read here by browsing on your ML that there exists an Opteron Bug, but I couldn't find any more info to this.
> So my question is: Is there a hardware bug in (SSE/2, anywhere) Opteron, is it fixed, was it related only to gromacs or could this affect any hand-coded assembly?
Yes there seems to be a hardware bug  in all SSE capable Athlons, but if
I am informed correctly gromacs 3.2.1 has a workaround. The bug was in
an obscure instruction relating to using unaligned memory. It is very
unlikely that this affects other code, as compilers tend to avoid such
instructions for performance reasons.

I think that Opterons are a good choice (I have some myself and posted
benchmarks last fall).

> Thanx in advance for your replies :-)
> Best regards,
> Thomas
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David van der Spoel, PhD, Assist. Prof., Molecular Biophysics group,
Dept. of Cell and Molecular Biology, Uppsala University.
Husargatan 3, Box 596,  	75124 Uppsala, Sweden
phone:	46 18 471 4205		fax: 46 18 511 755
spoel at xray.bmc.uu.se	spoel at gromacs.org   http://xray.bmc.uu.se/~spoel

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