[Beowulf] General thoughts on Xeon 56xx versus E5 series?

Igor Kozin i.n.kozin at googlemail.com
Fri Sep 14 04:00:06 PDT 2012


if memory bandwidth is your concern then there are models which boost
it quite significantly. e.g.
http://ark.intel.com/products/64584/Intel-Xeon-Processor-E5-2660-20M-Cache-2_20-GHz-8_00-GTs-Intel-QPI
probably very few codes are going to benefit from AVX without extra
efforts but BW is a clear win.
i'm seeing a good speed up on some applications which can be
attributed to higher BW.

On 13 September 2012 15:48, Orion Poplawski <orion at cora.nwra.com> wrote:
> On 09/13/2012 08:09 AM, holway at th.physik.uni-frankfurt.de wrote:
>>> Any general thought out there on Xeon 56xx versus E5 performance wise?
>>
>> We were comparing the performance of an older AMD with a newer AMD a while
>> ago and found that the newer AMDs floating point performance was
>> significantly reduced.
>>
>> It turned out that the kernel did not yet support AVX or FMA4 or some
>> other new fancy bit of register blah blah so it reverted to some
>> compatibility support for floating point operations. (I am not a kernel
>> dev :)
>>
>> If your going to play with newer processors you have to make sure your
>> kernel supports all the functions of that CPU. Kernel development can be a
>> little way behind on mainstream releases.
>>
>> Ta,
>>
>> Andrew
>
> Thanks for the reminder of kernel support.  RedHat states that RHEL5.7 should
> support the E5 processors, so hopefully that means supporting the new
> instructions.
>
> It seems the question before us is core scaling versus raw MHz.  I've seen
> many codes saturate the memory bandwidth before filling all of the cores and
> it seems you have a trade off between MHz and cores these days at a given
> price point.  But perhaps that doesn't even matter if you're memory bandwidth
> limited anyways.
>
>
> --
> Orion Poplawski
> Technical Manager                     303-415-9701 x222
> NWRA, Boulder Office                  FAX: 303-415-9702
> 3380 Mitchell Lane                       orion at nwra.com
> Boulder, CO 80301                   http://www.nwra.com
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