[Beowulf] Engineers boost AMD CPU performance by 20% without overclocking

Rayson Ho raysonlogin at gmail.com
Tue Feb 28 08:57:59 PST 2012


The paper is now available online, "CPU-Assisted GPGPU on Fused
CPU-GPU Architectures":

http://people.engr.ncsu.edu/hzhou/hpca_12_final.pdf

(I have not read the whole paper yet) I think the core idea is that
the CPU acts as a prefetch thread and pulls data into the shared L3
for the GPU cores (this work is like other prefetch thread research
projects that use the otherwise spare SMT threads to do prefetching
for the main compute thread), and as the GPU cores get more cache
hits, the performance is better (hence the 20% mentioned in the
extremetech article).

Rayson

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On Fri, Feb 10, 2012 at 12:48 PM, Vincent Diepeveen <diep at xs4all.nl> wrote:
> Another interesting question is how a few cores cores would be able
> to speedup
> a typical single precision gpgpu application by 20%.
>
> That would means that the gpu is really slow, especially if we
> realize this is just 1 or 2 CPU cores or so.
>
> Your gpgpu code really has to kind of be not so very professional to
> have 2 cpu cores alraedy contribute
> some 20% to that.
>
> Most gpgpu codes here on a modern GPU you need about a 200+ cpu cores
> and that's usually codes which
> do not run optimal at gpu's, as it has to do with huge prime numbers,
> so simulating that at a 64 bits cpu is more
> efficient than a 32 bits gpu.
>
> So in their case the claim is that for their experiments, assuming 2
> cpu cores, that would be 20%. Means we have a
> gpu that's 20x slower or so than a fermi at 512 cores/HD6970 @ 1536.
>
> 1536 / 20 = 76.8 gpu streamcores. That's AMD Processing Element
> count. for nvidia this is similar to 76.8 / 4 = 19.2 cores
>
> This laptop is from 2007, sure it is a macbookpro 17'' apple, has a
> core2 duo 2.4Ghz and has a Nvidia GT 8600M with 32 CUDA cores.
>
> So if we extrapolate back, the built in gpu is gonna kick that new
> AMD chip, right?
>
> Vincent
>
> On Feb 10, 2012, at 6:08 PM, Joe Landman wrote:
>
>> On 02/10/2012 12:00 PM, Lux, Jim (337C) wrote:
>>> Expecting headlines to be accurate is a fool's errand...
>>> Be glad it actually said AMD.
>>
>> Expecting articles contents to reflect in any reasonable way upon
>> reality may be a similar problem.  There are a few, precious few
>> writers
>> who really grok the technology because they live it:  Doug Eadline,
>> Jeff
>> Layton, Henry Newman, Chris Mellor, Dan Olds, Rich Brueckner, ... .
>>
>> The vast majority of articles I've had some contact with the
>> authors on
>> (not in the above group) have been erroneous to the point of being
>> completely non-informational.
>>
>>
>>
>> --
>> Joseph Landman, Ph.D
>> Founder and CEO
>> Scalable Informatics Inc.
>> email: landman at scalableinformatics.com
>> web  : http://scalableinformatics.com
>>         http://scalableinformatics.com/sicluster
>> phone: +1 734 786 8423 x121
>> fax  : +1 866 888 3112
>> cell : +1 734 612 4615
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