[Beowulf] ECC

Douglas Eadline deadline at eadline.org
Mon Nov 5 09:23:48 PST 2012


> Am 05.11.2012 um 17:50 schrieb Douglas Eadline:
>
>> --snip--
>>
>>>>
>>>> More interesting is the ECC discussion.
>>>>
>>>> ECC is simply a requirement IMHO, not a 'luxury thing' as some
>>>> hardware engineers see it.
>>>
>>> Depends on your computational model.  Would you rather spend money on
>>> ECC
>>> or on more processors?
>>> ECC comes at a cost in speed as well.  There is some non-zero time
>>> required to compute the syndrome bits and do the correction on the
>>> read.
>>> Sure, you can pipeline it, but there's some extra latency inevitably
>>> added.
>>>
>>
>> I find it interesting that many users thought GPU's could not be
>> a research tool unless they had ECC memory. I have one associate who
>> turns it off because they get 10% better performance on their
>> Amber runs.
>
> Turned if off in the BIOS or installed non-registered memory? With my
> tests I couldn't see any difference in execution time whether the
> installed ECC memory is switched off or on (or even which type of error
> correction I set up in the BIOS). Comparing registered and non-registered
> memory would be a more understandable difference in execution time.
>
> Several CPUs also slow down memory access if many DIMMs are installed, so
> it seems to be better to use larger and hence fewer memory modules - which
> might be more expensive though.

Turned off in GPU BIOS, see bottom of page:

  http://ambermd.org/gpus/#Max_Perf

--
Doug


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Doug

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