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-   -   Core i7 920 2.66ghz vs. 2x Xeon e5420 2.5 ghz (

CaglarCoskun January 31, 2013 08:50

Core i7 920 2.66ghz vs. 2x Xeon e5420 2.5 ghz
I have a computer having a Core i7 920 processor (4 cores and 8 threads) with 16gb of RAM, running a FLUENT case file having about 14 million meshes.
I have another computer, which is a Dell workstation having dual Xeon e5420 processors (4 cores and 4 threads per processor) with 24gb RAM and this computer runs another FLUENT case having about 16 million meshes.
These case files are physically very similar. The problem is the second computer (Dell) is considerably slower than the first one. I measured the iteration times, and the first computer (i7) calculates an iteration in about 40 seconds and the other one calculates about 190 seconds! The parallel processing is enabled in both case files to 8 processors.
Is this normal? or what might be the cause of this slowness?

Note: The operating systems and ANSYS versions are also the same (Windows 7 Professional and ANSYS 14.0)

scipy January 31, 2013 13:36

Old E5420 Xeon = single channel DDR2 memory.
Newer i7 920 = triple channel DDR3 memory.

That's the difference. :) And before you ask, yes - it can be that drastic/high/huge. However, a newer i5 (22 nm) with 4 cores and dual channel DDR3 would be faster than both of these (and more power efficient), while a new i7 3930K (32 nm) with quad channel DDR3 would literally be several times faster than both of your PCs combined.

Time to trade in the old hardware, it only looks impressive on paper. :)

CaglarCoskun January 31, 2013 13:57


I know the i7 is newer and introduce some new technologies, but the performance gap between them in CFD calculations is really surprising for me =)

Another strange point is, according to the Windows experience index, while the subscore of 2x Xeon is 7.6, the subscore of i7 920 is 7.4 =) It may not be a reliable tool for benchmarking, but the result is intresting.

scipy January 31, 2013 14:56

Windows experience index is determined by the lowest subscore in any category, so it's not that trustworthy.

As far as CFD performance goes - the memory speed and bandwith is the most prominent factor, and this is where the newer stuff is mostly different and where most of the improvements come from.

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