Which processor best for HPC?

[umar]

Hi, I am a bit confused about the new Nehalem processors. Trying to buy a new
Dell Precision system. I have a couple of QX9650 systems but the new ones are
all Xeon's.

My calculations are heavy on floating-point and large in memory usage. Which
cache is better here? L2 or L3? Is the W5580 a good processor compared to
i-965?

I presume intel fortran 11.x will be supporting these processors. Any becnhmarks
for HPC calculations. Thanks.

[TimP]

The Xeon 5500 series HPC benchmarks are prominent on Intel publicity pages
http://www.intel.com/performance/server/xeon/hpc.htm?iid=perf_server+dp_hpc
and on the standard benchmark sites for the selected applications.
The wikipedia article doesn't appear to include the multiple socket Nehalem Xeon processors (note that the Intel marketing term is far more verbose).
Dell has had apparently excellent Core i7-920 models in their catalog for several weeks. These have not been promoted for HPC; this single socket model may match the performance of the Harpertown dual socket server models, which some vendors hope to continue selling. Contrary to the Dell catalog offerings, you would want at least 2GB RAM sticks for HPC, and you may wish to consider configurations which keep 3 memory channels active.
The range of linux distros which are easy to install remains somewhat limited; unfortunately, there is no integrated video adaptor in Core i7 support chipsets so far.
www.topcrunch.org shows benchmarks for 1 and 2 node clusters of Core i7-920, along with many Xeon 5500 and the older 5450.
ifort 11.0 has an option specific to SSE4.2, but it is unlikely to improve performance over SSE4.1.
Multiple CPU vendors have converged on the 3 level cache with unified higher level cache. It usually gives excellent support for combined OpenMP and vectorization. The weakness shows up when there is poor data page locality, when all data access goes to last level cache.

[jimdempseyatthecove]

>>unfortunately, there is no integrated video adaptor in Core i7 support chipsets so far.

Tim, on all my systems I have disabled the on board video as this sucks too much off the system performance. A low end graphics card (~$50) can return significant performance.

On my server box (2 x Opteron 270 (4 cores)) with a command window open (Windows Server 2003) when using on-board video performing a simple "DIR C: /S" sucked 25% of the system processing (consumed all of one core). Inserting a low end e-Geforce MX-4000 PCI video card (128MB) the same test is under 1%. A similar performance difference on my Intel Q6600 system. Your Milage May Vary. Granted, if the system is doing nothing, then the video is not a problem. The other advantageis most low-end video cards are now dual head.

I view the integrated video adapter as a negative.

Jim Dempsey

[TimP]

Jim,
I was referring to ease of installing linux. If you had a video card which isn't supported by a Windows driver, you would expect your money back. What a waste, to put in a video card which uses 50% of the power drain, and puts out so much hot air that the CPU overheats.

[jimdempseyatthecove]

Tim,

My (to date) experience with on-board video is they all suck processing capacity from your system (and some RAM). The use of just about any video card will recover this processing capacity. The original post on this thread was "Which processor best for HPC". My comments were directed at: If you are interested in HPC then consider using an add-in video card.

If you are concerned with power drain (in watts) then consider using a system based on the Atom processor, but then you would not be into HPC. If you are concerned about watts consumed as well as performance, then use the watts conumption for the card as selection chriteria (good luck at trying to locate this information).

BTW I haven't had a problem with overheating a processor regardless of video card.