Hi Ross,
first of all thanks a lot for your complex answer !
In fact I assume mainly independent single GPU jobs. So if I understood
well, in such case there should not be problem considering below mentioned
motherboard/CPU/4xGPU. Am I right ?
Best wishes,
Marek
Dne Tue, 13 Sep 2011 18:53:34 +0200 Ross Walker <ross.rosswalker.co.uk>
napsal/-a:
> Hi Marek,
>
> I would say that the answer is, with caveats, not really. The reason for
> this is not a core to GPU ratio argument per se but actually one of
> memory
> bandwidth. For a single socket motherboard there is no way that it can
> drive
> 4 PCI-E sockets flat out at x16 speed. Hence you are always going to get
> contention. Typically I would say never go beyond 2 GPUs per node for a
> single socket system. 4 GPUs per node is pushing it for a dual socket
> system
> even with the highest CPU FSB speed you can get so on a single socket
> system
> with a low end CPU it is definitely not going to cut it.
>
> Now if you only plan to run single GPU jobs. I.e. 4 independent jobs at
> once
> with reasonably large values for ntpr, ntwx etc then it is probably not
> an
> issue since the memory bandwidth only really comes into play at each
> output
> file or trajectory write for most types of calculations. However, trying
> to
> run in parallel where a single job spans GPUs it really all comes down
> to a
> combination of the aggregate memory bandwidth of the main CPU memory per
> GPU
> and the PCI-E bandwidth to each GPU when all are communicating flat out
> at
> the same time. You might be able to get speedup across 2 of the GPUs if
> you
> leave the other two idle. However, running two sets of dual GPU runs or
> running a single 4 GPU run is likely to cause so much contention that see
> little or no speedup.
>
> So it really comes down to a case of the type of jobs you want to run.
>
> I hope that helps.
>
> All the best
> Ross
>
>> -----Original Message-----
>> From: Marek Maly [mailto:marek.maly.ujep.cz]
>> Sent: Tuesday, September 13, 2011 7:19 AM
>> To: amber.ambermd.org
>> Subject: [AMBER] Sufficient CPU cores/GPU ratio ?
>>
>> Hi all,
>>
>> just a very quick technical question. I would like to know if 4 core
>> CPU
>> "Intel Core i7-960" might be sufficient for
>> 4 GPU machine (motherboard: Asus P6T7 WS SuperComputer - Intel X58 ).
>> I
>> mean if ratio 1 CPU core/ 1 GPU might
>> be here sufficient also considering some requirements (on CPU) for
>> managing operating system etc.
>>
>> Thanks in advance for any relevant comment !
>>
>> Best wishes,
>>
>> Marek
>>
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>> AMBER.ambermd.org
>> http://lists.ambermd.org/mailman/listinfo/amber
>
>
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Received on Tue Sep 13 2011 - 10:30:04 PDT
