Replies to post #8197 on Advanced Micro Devices Inc (AMD)

[Haddock]

find it surprising that Power4 and Itanium 2 both receive lousy scores on this benchmark

Here's more info on CTH and Alegra. It's not obvious to me either why I2 doesn't do better on them.

http://sherpa.sandia.gov/9231home/papers-frame.html

[chipguy]

Also, I think it's interesting to check out slide 53, which lists the relative performance on Sandia's apps. I
find it surprising that Power4 and Itanium 2 both receive lousy scores on this benchmark, but it is nice to
see that Sandia did their due diligence here. Based on other HPC apps that I have seen, I would have
thought that Power4 and Itanium 2 would achieve close to what EV7 could get, but on the other hand,
applications are not all created equal. There are simply some issues in the micro-architecture of a CPU
that will allow it to perform faster or slower in some situations, and Itanium 2 is clearly not the solution for
this project (at least, not without some major fine-tuning of the CTH and Alegra applications).

I was quite frankly shocked by the processor comparison data in this presentation. Clearly there
are factors here, real or artificial, that don't allow all the machines to perform up to their potential.
The EV7 is capable of only 2.3 GFLOP/s peak, the Itanium 2/1000 4.0 GFLOP/s peak. The huge
disparity presented here doesn't pass the smell test. I hate to sound like an conspiracy theorist but
it appears that the Sandia team cooked the tests. Why were I2 tests reported as "about the same as
P4@2GHz" instead of an actual number? Did they even bother to benchmark it? The national labs
are traditionally big Alpha boosters and this machine was architected in the bittermess and after
shock of Compaq killing off Alpha in favour of IPF. Anyway, this is a one-off custom machine. Far
more HPC work will be done on just the Altix 3000s that sell by the time Red Storm is operational.