[Beowulf] performance tweaks and optimum memory configs for a Nehalem

Joshua Baker-LePain jlb17 at duke.edu
Mon Aug 10 16:07:00 EDT 2009


On Mon, 10 Aug 2009 at 3:02pm, Rahul Nabar wrote

> On Mon, Aug 10, 2009 at 2:09 PM, Joshua Baker-LePain<jlb17 at duke.edu> wrote:
>> Well, as there are only 8 "real" cores, running a computationally intensive
>> process across 16 should *definitely* do worse than across 8. However, it's
>> not so surprising that you're seeing peak performance with 2-4 threads.
>>  Nehalem can actually overclock itself when only some of the cores are busy
>> -- it's called Turbo Mode.  That *could* be what you're seeing.
>
> That could very well be it! Is there any way to test if the CPU has
> overclocked itself?
>
> Or can I turn the "turbo mode" off and check?

You *should* be able to turn off turbo mode in the BIOS.

-- 
Joshua Baker-LePain
QB3 Shared Cluster Sysadmin
UCSF
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