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Redefining TDP With PowerTune

One of our fundamental benchmarks is FurMark, oZone3D’s handy GPU load testing tool. The furry donut can generate a workload in excess of anything any game or GPGPU application can do, giving us an excellent way to establish a worst case scenario for power usage, GPU temperatures, and cooler noise. The fact that it was worse than any game/application has ruffled both AMD and NVIDIA’s feathers however, as it’s been known to kill older cards and otherwise make their lives more difficult, leading to the two companies labeling the program a “power virus”.

FurMark is just one symptom of a larger issue however, and that’s TDP. Compared to their CPU counterparts at only 140W, video cards are power monsters. The ATX specification allows for PCIe cards to draw up to 300W, and we quite regularly surpass that when FurMark is in use. Things get even dicier on laptops and all-in-one computers, where compact spaces and small batteries limit how much power a GPU can draw and how much heat can effectively be dissipated. For these reasons products need to be designed to meet a certain TDP; in the case of desktop cards we saw products such as the Radeon HD 5970 where it had sub-5870 clocks to meet the 300W TDP (with easy overvolting controls to make up for it), and in laptop parts we routinely see products with many disabled functional units and low clocks to meet those particularly low TDP requirements.

Although we see both AMD and NVIDIA surpass their official TDP on FurMark, it’s never by very much. After all TDP defines the thermal limits of a system, so if you regularly surpass those limits it can lead to overwhelming the cooling and ultimately risking system damage. It’s because of FurMark and other scenarios that AMD claims that they have to set their products’ performance lower than they’d like. Call of Duty, Crysis, The Sims 3, and other games aren’t necessarily causing video cards to draw power in excess of their TDP, but the need to cover the edge cases like FurMark does. As a result AMD has to plan around applications and games that cause a high level of power draw, setting their performance levels low enough that these edge cases don’t lead to the GPU regularly surpassing its TDP.

This ultimately leads to a concept similar to dynamic range, defined by Wikipedia as: “the ratio between the largest and smallest possible values of a changeable quantity.” We typically use dynamic range when talking about audio and video, referring to the range between quiet and loud sounds, and dark and light imagery respectively. However power draw is quite similar in concept, with a variety of games and applications leading to a variety of loads on the GPU. Furthermore while dynamic range is generally a good thing for audio and video, it’s generally a bad thing for desktop GPU usage – low power utilization on a GPU-bound game means that there’s plenty of headroom for bumping up clocks and voltages to improve the performance of that game. Going back to our earlier example however, a GPU can’t be set this high under normal conditions, otherwise FurMark and similar applications will push the GPU well past TDP.

The answer to the dynamic power range problem is to have variable clockspeeds; set the clocks low to keep power usage down on power-demanding games, and set the clocks high on power-light games. In fact we already have this in the CPU world, where Intel and AMD use their turbo modes to achieve this. If there’s enough thermal and power headroom, these processors can increase their clockspeeds by upwards of several steps. This allows AMD and Intel to not only offer processors that are overall faster on average, but it lets them specifically focus on improving single-threaded performance by pushing 1 core well above its normal clockspeeds when it’s the only core in use.

It was only a matter of time until this kind of scheme came to the GPU world, and that time is here. Earlier this year we saw NVIDIA lay the groundwork with the GTX 500 series, where they implemented external power monitoring hardware for the purpose of identifying and slowing down FurMark and OCCT; however that’s as far as they went, capping only FurMark and OCCT. With Cayman and the 6900 series AMD is going to take this to the next step with a technology called PowerTune.

PowerTune is a power containment technology, designed to allow AMD to contain the power consumption of their GPUs to a pre-determined value. In essence it’s Turbo in reverse: instead of having a low base clockspeed and higher turbo multipliers, AMD is setting a high base clockspeed and letting PowerTune cap GPU performance when it exceeds AMD’s TDP. The net result is that AMD can reduce the dynamic power range of their GPUs by setting high clockspeeds at high voltages to maximize performance, and then letting PowerTune cap GPU performance for the edge cases that cause GPU power consumption to exceed AMD’s preset value.

Advancing Primitives: Dual Graphics Engines & New ROPs PowerTune, Cont
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  • B3an - Thursday, December 16, 2010 - link

    Very stupid uninformed and narrow-minded comment. People like you never look to the future which anyone should do when buying a graphics card, and you completely lack any imagination. Theres already tons of uses for GPU computing, many of which the average computer user can make use of, even if it's simply encoding a video faster. And it will be use a LOT more in the future.

    Most people, especially ones that game, dont even have 17" monitors these days. The average size monitor for any new computer is at least 21" with 1680 res these days. Your whole comment is as if everyone has the exact same needs as YOU. You might be happy with your ridiculously small monitor, and playing games at low res on lower settings, and it might get the job done, but lots of people dont want this, they have standards and large monitors and needs to make use of these new GPU's. I cant exactly see many people buying these cards with a 17" monitor!
    Reply
  • CeepieGeepie - Thursday, December 16, 2010 - link

    Hi Ryan,

    First, thanks for the review. I really appreciate the detail and depth on the architecture and compute capabilities.

    I wondered if you had considered using some of the GPU benchmarking suites from the academic community to give even more depth for compute capability comparisons. Both SHOC (http://ft.ornl.gov/doku/shoc/start) and Rodinia (https://www.cs.virginia.edu/~skadron/wiki/rodinia/... look like they might provide a very interesting set of benchmarks.
    Reply
  • Ryan Smith - Thursday, December 16, 2010 - link

    Hi Ceepie;

    I've looked in to SHOC before. Unfortunately it's *nix-only, which means we can't integrate it in to our Windows-based testing environment. NVIDIA and AMD both work first and foremost on Windows drivers for their gaming card launches, so we rarely (if ever) have Linux drivers available for the launch.

    As for Rodinia, this is the first time I've seen it. But it looks like their OpenCL codepath isn't done, which means it isn't suitable for cross-vendor comparisons right now.
    Reply
  • IdBuRnS - Thursday, December 16, 2010 - link

    "So with that in mind a $370 launch price is neither aggressive nor overpriced. Launching at $20 over the GTX 570 isn’t going to start a price war, but it’s also not so expensive to rule the card out. "

    At NewEgg right now:

    Cheapest GTX 570 - $509
    Cheapest 6970 - $369

    $30 difference? What are you smoking? Try $140 difference.
    Reply
  • IdBuRnS - Thursday, December 16, 2010 - link

    Oops, $20 difference. Even worse. Reply
  • IdBuRnS - Thursday, December 16, 2010 - link

    570...not 580...

    /hangsheadinshame
    Reply
  • epyon96 - Thursday, December 16, 2010 - link

    This was a very interesting discussion to me in the article.

    I'm curious if Anandtech might expand on this further in a future dedicated article comparing what NVIDIA is using to AMD.

    Are they also more similar to VLIW4 or VLIW5?

    Can someone else shed some light on it?
    Reply
  • Ryan Smith - Thursday, December 16, 2010 - link

    We wrote something almost exactly like you're asking for for our Radeon HD 4870 review.

    http://www.anandtech.com/show/2556

    AMD and NVIDIA's compute architectures are still fundamentally the same, so just about everything in that article still holds true. The biggest break is VLIW4 for the 6900 series, which we covered in our article this week.

    But to quickly answer your question, GF100/GF110 do not immediately compare to VLIW4 or VLIW5. NVIDIA is using a pure scalar architecture, which has a number of fundamental differences from any VLIW architecture.
    Reply
  • dustcrusher - Thursday, December 16, 2010 - link

    The cheap insults are nothing but a detriment to what is otherwise an interesting argument, even if I don't agree with you.

    As far as the intellect of Anandtech readers goes, this is one of the few sites where almost all of the comments are worth reading; most sites are the opposite- one or two tiny bits of gold in a big pan of mud.

    I'm not going to "vastly overestimate" OR underestimate your intellect though- instead I'm going to assume that you got caught up in the moment. This isn't Tom's or Dailytech, a little snark is plenty.
    Reply
  • Arnulf - Thursday, December 16, 2010 - link

    When you launch an application (say a game), it is likely to be the only active thread running on the system, or perhaps one of very few active threads. CPU with Turbo function will clock up as high as possible to run this main thread. When further threads are launched by the application, CPU will inevitably increase its power consumption and consequently clock down.

    While CPU manufacturers don't advertise this functionality in this manner, it is really no different from PowerTune.

    Would PowerTune technology make you feel any better if it was marketed the other way around, the way CPUs are ? (mentioning lowest frequencies and clock boost provided that thermal cap isn't met yet)
    Reply

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