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geoff · Joined: 18 Sep 2006 Posts: 1

In a discussion with Salford support a few years back, I was told that FTN95 worked better on Athlon than Intel processors. My codes certainly ran considerably faster on Athlon machines than on Intels with the same clock speed. Is this still the case? Does anyone have any current experience - with Intel Core Duo for instance?

Geoff

JohnCampbell · Joined: 16 Feb 2006 Posts: 2554 Location: Sydney

Geoff,
I can't help with the question, but I would also like to see an answer !!

silverfrost · Posted: Wed Sep 20, 2006 6:30 am Post subject: Athlon vs Intel

The Intel Duo and AMD X2 have multiple CPUs in a single package. The advertising of these processors -- and Intel's in particular has been a bit misleading, implying that programs will run quicker. Most programs, Fortran code in particular, is serial and runs on one thread. This thread will only run on one of the CPUs (hopefully anyway, moving the thread between CPUs is not efficient) and so will run no faster. However, the Operating System and other tasks will be spread across the two CPUs reducing the overall load... so the programs may run a little quicker on a similarly specified single CPU machine.

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Anonymous · Guest

Thanks for this. Leaving aside then the dual core issue, presumably it is still true in general that FTN95 runs faster on AMD chips than on Intels. The bottom line of course is: what PC do I buy to get the best performance!

Geoff

weaverwb · Joined: 04 Aug 2005 Posts: 37 Location: Monterey

So far, for my radiative transfer code, my opteron has been faster than my Xeon. I don't have quantitative info on that yet and issues like SSE utilization, etc. count, too. My code is mostly double precision. Floating point benchmarks (PC wizard) claim that the Opteron is significantly faster but I'm hoping to quantize the difference for my code in the next week or two. Note that I was also test Absoft, which was much slower than FTN95 which turned out to be the NINT calls. With that resolved, they're about the same speed! The Xeon is a dual processor, the Opteron is a dual-core.

Bruce Weaver
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silverfrost · Posted: Thu Sep 21, 2006 10:08 am Post subject: Athlon vs Intel

It is not necessarily that simple an issue. If you look at the current range of Intel processors you can buy:

Intel P4 Prescott
Intel P4 Northwood
Intel P4 Dual Core
Intel P4 Dual Core Conroe
Intel Xeon

This list ignores the Celeron range! There are enough differences of cache, clock speed and bus speed to make it very difficult to predict how fast your application will run. A Fortran loop might run quite a bit quicker on any of the above.

The simple answer is we cannot tell you Smile

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