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AVX Base vs. AVX Turbo

JJoha8
New Contributor I
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The documunt here (http://www.intel.com/content/dam/www/public/us/en/documents/specification-updates/xeon-e5-v3-spec-update.pdf http://www.intel.com/content/dam/www/public/us/en/documents/specification-updates/xeon-e5-v3-spec-update.pdf) states that a Xeon E5-2699 v3 Haswell-EP chip has an AVX Base Frequency of 1.9 GHz and an "AVX Turbo Boost Technology Maximum Core Frequency" (called AVX Turbo in the remainder of my post) of 2.6 GHz when using all 18 cores.

How do I compute the peak DP GFlop/s for this chip? Assuming 1.9 GHz I arrive at 1.9 [GHz] * 18 [cores] * 2 [two FMA units] * 4 [AVX] * 2 [FMA] = 547.2 GFlop/s. Assuming 2.6 GHz I get 748.8. In some documents it says the Turbo can only be achieved for "most AVX" workloads (whatever that is). What factors impact whether my code qualifies to be included in "most AVX" workloads?

I tested a chip using a dot product benchmark which issues two AVX loads and two AVX FMAs per cycle with a dataset in the L3 cache running on all cores which, according to RAPL counters, went over the TDP. However, the measured frequency was still 2.6 GHz. IMO a workload can't get much worse than that for the chip. Is it perhaps dependent on the quality of the chip whether my code will run at something below 2.6 GHz? In that case, depending on the chip quality, some people would get a chip that offers 30% more performance vs the one that can only do AVX base. That doesn't sound right. Can someone please clarify?

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idata
Employee
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JJoha8
New Contributor I
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Thanks for the pointers. I have a simple follow-up question that maybe summarises my previous questions:

According to Table-3 in http://www.intel.com/content/dam/www/public/us/en/documents/specification-updates/xeon-e5-v3-spec-update.pdf http://www.intel.com/content/dam/www/public/us/en/documents/specification-updates/xeon-e5-v3-spec-update.pdf a Xeon E5-2595 v3 has an Intel AVX Frequency of 1.9 GHz and an AVX Turbo Frequency of 2.6 GHz when running on all cores.

Now I'm running a fixed workload x on a E5-2595 v3 chip using all cores and via performance counters measure a CPU frequency of 2.6 GHz.

Will the same workload obtain 2.6 GHz on all chips of that model?

Thanks,

Johannes

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idata
Employee
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As far as I can see, based on the chart you are pointing at. It seems all E5-2595 will perform the same.

 

I recommend keep checking this thread for different community members that may help you with additional details.

 

 

Allan.
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