Power Optimizations

It is well known that the Haswell has been optimized for low idle power. Servers run at idle a lot less than mobile devices and thus more power management capabilities were needed. 

In Haswell EP, Intel introduces per core p-states (PCPS). PCPS is not necessarily a blessing, as a wrongly chosen p-state can result in higher response times. However, Intel is convinced PCPS will save power or will at least shift the power to where it is needed: to other cores or to the uncore (rings). 

Floating Point intensive code is known to cause power peaks. AVX has doubled the theoretical FLOPS, and the FMA (Fused Multiply Add) of AVX 2.0 promises to double it again. 

To cope with the huge difference between the power consumption of Integer and AVX code, Intel is introducing new base and Turbo Boost frequencies for all their SKUs; these are called AVX base/Turbo. For example, the E5-2693 v3 will start from a base frequency of 2.3GHz and turbo up to 3.3GHz when running non-AVX code. When it encounters AVX code however, it will not able to boost its clock to more than 3GHz during a 1 ms window of time. If the CPU comes close to thermal and TDP limits, clock speed will drop down to 1.9GHz, the "AVX base clock".

Here, Intel illustrates how this will work for their top SKU, the Xeon E5-2699 v3. Notice the lower base clock for AVX code (1.9 vs 2.3).

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View All Comments

  • KAlmquist - Monday, September 08, 2014 - link

    Also, the 2637 v2 is 4/8, not 6/12. Reply
  • isa - Monday, September 08, 2014 - link

    Looking forward to a new supercomputer record using these behemoths. Reply
  • Bruce Allen - Monday, September 08, 2014 - link

    Awesome article. I'd love to see Cinebench and other applications tests. We do a lot of rendering (currently with older dual Xeons) and would love to compare these new Xeons versus the new 5960X chips - software license costs per computer are so high that the 5960X setups will need much higher price/performance to be worth it. We actually use Cinema 4D in production so those scores are relevant. We use V-Ray, Mental Ray and Arnold for Maya too but in general those track with the Cinebench scores so they are a decent guide. Thank you! Reply
  • Ian Cutress - Monday, September 08, 2014 - link

    I've got some E5 v3 Xeons in for a more workstation oriented review. Look out for that soon :) Reply
  • fastgeek - Monday, September 08, 2014 - link

    From my notes a while back... two E5-2690 v3's (all cores + turbo enabled) under 2012 Server yielded 3,129 for multithreaded and 79 for single.

    While not Haswell, I can tell you that four E5-4657L V2's returned 4,722 / 94 respectively.

    Hope that helps somewhat. :-)
  • fastgeek - Monday, September 08, 2014 - link

    I don't see a way to edit my previous comment; but those scores were from Cinebench R15 Reply
  • wireframed - Saturday, September 20, 2014 - link

    You pay for licenses for render Nodes? Switch to 3DS, and you get 9999 nodes for free (unless they changed the licensing since I last checked). :) Reply
  • Lone Ranger - Monday, September 08, 2014 - link

    You make mention that the large core count chips are pretty good about raising their clock rate when only a few cores are active. Under Linux, what is the best way to see actual turbo frequencies? cpuinfo doesn't show live/actual clock rate. Reply
  • JohanAnandtech - Monday, September 08, 2014 - link

    The best way to do this is using Intel's PCM. However, this does not work right now (only on Sandy and Ivy, not Haswel) . I deduced it from the fact that performance was almost identical and previous profiling of some of our benchmarks. Reply
  • martinpw - Monday, September 08, 2014 - link

    There is a nice tool called i7z (can google it). You need to run it as root to get the live CPU clock display. Reply

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