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

[Orion Poplawski]

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
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