[Beowulf] Athlon64 / Opteron test

Daniel Fernandez daniel at labtie.mmt.upc.es
Mon May 17 11:27:15 PDT 2004

What kind of applications are you running ? Just only to get a reference
regarding our "theorical" future performance running our code on an

As a side note there's the power that the Opteron processor draws from
the power supply , supposedly less than an Athlon at same clockspeed. I
think a standard ATX 300W one should suffice for one Opteron, memory and
a small harddisk. ¿ Are you using any other kind of power supply for
AMD64 platforms ?


Daniel Fernandez <daniel at labtie.mmt.upc.es>
Heat And Mass Transfer Center - CTTC
c/ Colom nº11
UPC Campus Industrials Terrassa , Edifici TR4

On Fri, 2004-05-14 at 02:06, Robert G. Brown wrote:
> On Thu, 13 May 2004, Daniel Fernandez wrote:
> > Hi,
> > 
> > We're studying the possibility of installing a 64 bit testing node.
> > 
> > The main purpose is about getting impressions related to the
> > increase we would obtain in our particular scenario, computational
> > dynamics.
> > 
> > In order to do the test, we have no doubt about the OS: Red Hat
> > Enterprise 3, but we are a bit confused about the harware of choice:
> > 
> >             Athlon64
> >             Opteron
> > 
> > As far as we know, Opteron has two main differences:
> > 
> >     - A wider memory interface (128 bit in front of 64)
> >     - A larger L2 cache memory (1 Mb)
> > 
> > Before doing any test, the questions are:
> > 
> > 1)
> > 
> >  Which is the theoretical maximum performance gain using full 64 bit
> > architecture in front of 32 bit, taking into account that our
> > computations are done in double precision floating point using
> > big matrices?
> I don't know what theoretical maximum gain means -- something with
> multiplying out clocks, pipeline form factors, datapath widths, and
> assuming perfect state?  Never happens, more or less useless number.
> I do have a moderate amount of faith in what process-specific
> microbenchmarks like stream and lmbench tell one (not as much as one
> might think, but some useful data points).  I also have a LOT of faith
> in using your own application as a benchmark on a loaner machine (or
> machines).  So much so that this is one of the points of focus of my
> next couple of Cluster World columns -- the importance of
> your application and the deep significance of "YMMV" when asking other
> people what to buy.
> If stream or stream-like microbenchmarks would be of any use to you, I
> have Opterons but not Athlon64's handy.  Maybe somebody else can do
> other for you.  Remember, though, that even these results may vary
> significantly with compiler, with link libraries, with WHICH Opteron
> motherboard you get and how memory is loaded onto the motherboard.  It
> is very, very difficult to get portable numbers without a prototyping
> machine that is "like" the architecture you are considering in very
> specific form (ideally, identical).
> > 2)
> > 
> > Is it nowadays the 64 bit solution using Linux ready for production?
> > If this is the case, which problems may we have to deal with in
order to
> > compile and run our code in a full 64 bit environment?
> I'm using dual Opterons (Penguin Altus 1000E's) running Fedora right
> without any major problems.  Your two problems are likely to be
> rebuilding things that aren't for some reason in the Fedora core and
> already built for the Opteron.  So far I haven't encountered any major
> problems compiling gcc-based code linked to the GSL and other
> useful/standard libraries.  YMMV, but a lot of people have these boxes
> now and together they form a powerful force pushing for full and clean
> distros, so even if you find something that doesn't work it likely
> work and at worst you might have to help make it work in the best of
> open source tradition, if it is in your key work pathway.
> We're likely to buy nothing else for cluster nodes in the medium run.
> So far they are by far the cost-benefit winner.
> > 3)
> > 
> > Which is the most mature solution: AMD Opteron or Intel Itanium?
> Did you mean mature or moribund;-)?  
> I'm only half kidding.  Itanium is dead as a doornail as technology
> -- overpriced, underperforming, incompatible.  Intel is migrating to a
> (more or less) Opteron compatible 64 bit processor as fast as they can
> get there, as Major Software Companies (MSC) have announced that they
> aren't going to do major ports to new chips with new machine languages
> and compilers anymore if they can possibly avoid it.  If Intel dropped
> the price of an Itanium to slightly LESS than that of an Opteron, I
> think they'd still have trouble maintaining a market, because Opterons
> are relatively easy to port to and will in principle run i386 code
> (badly, of course) native.  Sometimes.  I haven't had a lot of luck
> it, of course, because you can't mix i386 code and 64 bit DLLs and we
> installed a 64 bit version of the OS from the start, but theoretically
> it will work.
> The good news is that Opterons are surprisingly fast for MY
> for their relatively pokey CPU clocks, and some benchmarks show that
> they can be really quite fast indeed for memory intensive applications
> relative to e.g. an Athlon or P4 clock.  They also run much cooler
> regular Athlons (again for my application).  I draw ballpark of 185
> watts loaded (dual CPU Opteron) vs 230 Watts or so loaded (dual CPU
> Athlon) running more or less the same code.
>    rgb

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