ATHLON vs XEON: number crunching

Thomas Guignon guignon at artabel.net
Fri Jun 21 11:31:44 EDT 2002


Le Jeudi 20 Juin 2002 15:06, vous avez écrit :
> Hi Steffen,
>
> Looking at your numbers I can make a conclusion that loading 2 processors
> on Xeon simply slows down the stream as for Athlon it does not and they
> are quite close to each other in case of full load of the node. Are you
> saying that the real test would be to run TWO IDENTICAL codes on the same
> node to load both processors?
>
> Ivan

Hello
I would be interesting to know which compiler was used for this stream 
benchmark? probably is the Intel compiler.
It's possible to improve the AMD numbers if prefetch is not in use but it 
will change the scalability conclusion of  Ivan Oleynik
The fact that dual Xeon perf decrease is quite strange (no speedup would be 
more normal) and there is some investigation to do:
- Does the  2 processors test was obtained with openMP (I guess it is) ?

> ------------------------------------------------------------------------
>
> On Thu, 20 Jun 2002, Steffen Persvold wrote:
> > Well, the E7500 chipset has two DDR _channels_ while the AMD762 system
> > controller has one DDR _channel_. One DDR channel is 64bit + ECC and is
> > normally running at 133MHz which gives us a theoretical peak performance
> > of 2.1 GBytes/sec per channel. However, the E7500 chipset is only able to
> > run the memory bus at 100MHz and with the interleaving of the two
> > channels that gives us a theoretical peak performance of 3.2 GBytes/sec.
> >
> > I believe the term "banks" is related to the layout of the DIMMs and has
> > nothing to do with the architecture of the system controller.
> >
> > Here are some stream numbers. The Athlon platform is Tyan S2466 equipped
> > with two Athlon MP 1900+ (1.6 GHz), and the Xeon platform is SuperMicro
> > P4DPR-6GM+ equipped with two Xeon 1.8 GHz (Prestonia).
> >
> > Athlon, 1 process :
> >
> > Function     Rate (MB/s)  Avg time   Min time  Max time
> > Copy:        877.5785      0.0365      0.0365      0.0367
> > Scale:       801.7857      0.0400      0.0399      0.0402
> > Add:         894.9042      0.0537      0.0536      0.0539
> > Triad:       887.2120      0.0542      0.0541      0.0544
> >
> > Athlon, 2 processes :
> >
> > Function     Rate (MB/s)  Avg time   Min time  Max time
> > Copy:       1385.1016      0.0236      0.0231      0.0253
> > Scale:      1345.9527      0.0242      0.0238      0.0250
> > Add:        1168.2247      0.0419      0.0411      0.0425
> > Triad:      1210.0117      0.0405      0.0397      0.0473
> >
> >
> > Xeon, 1 process :
> >
> > Function     Rate (MB/s)  Avg time   Min time  Max time
> > Copy:       1898.8954      0.0170      0.0169      0.0181
> > Scale:      1813.9614      0.0179      0.0176      0.0186
> > Add:        1839.8592      0.0265      0.0261      0.0274
> > Triad:      1826.2738      0.0266      0.0263      0.0274
> >
> > Xeon, 2 processes :
> >
> > Function     Rate (MB/s)  Avg time   Min time  Max time
> > Copy:       1160.5962      0.0297      0.0276      0.0311
> > Scale:      1261.8243      0.0269      0.0254      0.0275
> > Add:        1237.7180      0.0395      0.0388      0.0407
> > Triad:      1231.9053      0.0398      0.0390      0.0405
>
> ------------------------------------------------------------------------
> Ivan I. Oleynik                       E-mail : oleynik at chuma.cas.usf.edu
> Department of Physics
> University of South Florida
> 4202 East Fowler Avenue                  Tel : (813) 974-8186
> Tampa, Florida 33620-5700                Fax : (813) 974-5813
> ------------------------------------------------------------------------
>
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