Nehalem review up

Article: Nehalem Performance Preview
By: Vincent Diepeveen (diep.delete@this.xs4all.nl), April 12, 2009 2:01 am
Room: Moderated Discussions
Michael S (already5chosen@yahoo.com) on 4/11/09 wrote:
---------------------------
>Vincent Diepeveen (diep@xs4all.nl) on 4/11/09 wrote:
>---------------------------
>>Michael S (already5chosen@yahoo.com) on 4/10/09 wrote:
>>---------------------------
>>>Vincent Diepeveen (diep@xs4all.nl) on 4/10/09 wrote:
>>>---------------------------
>>>>Jack (jumpingjack6@verizon.net) on 4/9/09 wrote:
>>>>---------------------------
>>>>>Vincent Diepeveen (diep@xs4all.nl) on 4/7/09 wrote:
>>>>>
>>>>>>
>>>>>>How can you draw a conclusion about Shanghai, you haven't even compared it head on with Nehalem yourself.
>>>>>>
>>>>>>Vincent
>>>>>>
>>>>>
>>>>>David did characterize, at the beginning of the article, that Shanghai would be
>>>>>fairly characterize as slightly lagging harpertown, in that it falls behind in some
>>>>>cases, achieves parity and others, and has some strong points.
>>>>>
>>>>>Considering that is roughly a good assessment, then it can be extrapolated
>that Nehalem has opened up a wide margin.
>>>>>
>>>>>Nonentheless, you can search the databases yourself, the 5570 DP Xeon can range
>>>>>anywhere from 1.5 to 2x faster than a Shanghai 2P (2.7 GHz). I have not found one
>>>>>where Shanghai even comes close. This does not make Shanghai a bad CPU, but it
>>>>>does make it tough for AMD to market Shanghai against Nehalem.
>>>>
>>>>Sales ballony, based upon a few cracked spec tests.
>>>>
>>>>Both are nearly identical processors in performance for the software we tried.
>>>>
>>>>Of course HT and turboboost turned off, and Shanghai a tad higher clocked than
>>>>E versions of Xeon, gives Shanghai a slight edge in clockrate 2.53Ghz vs 2.7 shanghai.
>>>>Of course with more powerbudget intel clocks higher.
>>>>
>>>
>>>BTW, AMD submitted SpecJbb scores for 2.9GHz Shanghai. In the past it was the
>>>indication that next lower clocked part, i,e, 2.8GHz, will soon be available in
>>>normal thermal envelop. So there is a hope for 2.8GHz 75W Shanghai coming.
>>>
>>>>If you look to the intel documents in what i7 can execute it is SSE2+ instructions
>>>>a cycle max. That gives 8 flops as a max, with or without HT. Is that so much higher than AMD?
>>>>
>>>>Multiplication is not faster than at AMD in throughput, in fact if you try latencies
>>>>of AMD are better, so a good programmer CAN be faster at AMD.
>>>>
>>>
>>>Let's follow you own logic. Floating-point addition is faster (=had shorter latency)
>>>on Intel. Should we conclude that "a good programmer CAN be faster at Intel".
>>
>>There is 1 unit that is doing multiplication,
>>there is a lot that can do addition.
>>
>>Addition has a latency of 0.5 cycle at intel so to speak and 0.33 cycle or so at
>>AMD (i could be off by 0.17 or so as i checked the i7 handbooks quickly a while
>>ago for all kind of stuff, not the AMD ones).
>>
>
>Oh, I forgot that you don't that you don't understand the difference between latency and throughput.
>Sorry.
>But I didn't know that you don't understand the difference between integer and floating point addition :(
>Or may be you just plain don't know that bot Intel and AMD processors have only
>one (admittedly, wide) FP_ADD unit - 3-clock latency on Intel, 4 on AMD?
>
>>Multiplication is important for FFT
>
>
>Do you happen to know that Radix-2 butterfly consists of 6 additions ans 4 multiplications?
>Do you happen to know that each dependency chain in radix-2 butterfly includes 1 multiplication and 2 additions?
>
>>and matrix calculations.
>
>Where only addition is a part of long dependency chain so unrolling requirements
>(# of accumulators) depend solely on the latency of FP addition.
>
>>Adding goes rather
>>quick. Enough units to do it. Just 1 for multiplication.
>
>Why do you insist on talking about things you have zero clue about?
>
>

My qh library implements FFT for n bits FFT's total lossless, so without the usual FFT error that backtracks in floating point.

Apologies, Can you remind us which FFT codes you implemented?

I do not see you post in math forums either about all this.

Can you react onto the fact that i mentionned that there is a lot of execution units on the cpu that do addition, and that multiplication is dead slow on intel compared to addition?

On the throughput speed of intel cpu's we can speak another time, it is not so fast.
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TopicPosted ByDate
Nehalem review upDavid Kanter2009/04/07 02:43 AM
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                  Large pagesDavid Kanter2009/04/11 01:02 PM
                  Choice of C compiler doesn't matter much for Java...Henrik S2009/04/11 10:06 PM
                    Choice of C compiler doesn't matter much for Java...Paul2009/04/12 12:53 AM
                      Choice of C compiler doesn't matter much for Java...iz2009/04/12 01:59 AM
                      Choice of C compiler doesn't matter much for Java...Henrik S2009/04/12 06:37 AM
                    Choice of C compiler doesn't matter much for Java...EduardoS2009/04/12 07:08 AM
                      Choice of C compiler doesn't matter much for Java...Henrik S2009/04/12 08:25 AM
                        Choice of C compiler doesn't matter much for Java...EduardoS2009/04/12 04:24 PM
                          Choice of C compiler doesn't matter much for Java...Henrik S2009/04/12 09:18 PM
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                              Thread costsHenrik S2009/04/14 01:08 PM
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              Choice of C compiler doesn't matter much for Java...Henrik S2009/04/11 10:08 PM
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            Nehalem review upMichael S2009/04/11 04:12 PM
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                Nehalem review upMichael S2009/04/12 04:07 AM
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              Energy vs. powerJack2009/04/10 03:44 PM
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  Good work, i look forward to linux and SP2 numbers (NT)PiedPiper2009/04/08 12:52 AM
  Nehalem review upJoe Chang2009/04/10 02:59 AM
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