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Tweaking PowerTune

While the primary purpose of PowerTune is to keep the power consumption of a video card within its TDP in all cases, AMD has realized that PowerTune isn’t necessarily something everyone wants, and so they’re making it adjustable in the Overdrive control panel. With Overdrive you’ll be able to adjust the PowerTune limits both up and down by up to 20% to suit your needs.

We’ll start with the case of increasing the PowerTune limits. While AMD does not allow users to completely turn off PowerTune, they’re offering the next best thing by allowing you to increase the PowerTune limits. Acknowledging that not everyone wants to keep their cards at their initial PowerTune limits, AMD has included a slider with the Overdrive control panel that allows +/- 20% adjustment to the PowerTune limit. In the case of the 6970 this means the PowerTune limit can be adjusted to anywhere between 200W and 300W, the latter being the ATX spec maximum.

Ultimately the purpose of raising the PowerTune limit depends on just how far you raise it. A slight increase can bring a slight performance advantage in any game/application that is held back by PowerTune, while going the whole nine yards to 20% is for all practical purposes disabling PowerTune at stock clocks and voltages.

We’ve already established that at the stock PowerTune limit of 250W only FurMark and Metro 2033 are PowerTune limited, with only the former limited in any meaningful way. So with that in mind we increased our PowerTune limit to 300W and re-ran our power/temperature/noise tests to look at the full impact of using the 300W limit.

Radeon HD 6970: PowerTune Performance
PowerTune 250W PowerTune 300W
Crysis Temperature 78 79
Furmark Temperature 83 90
Crysis Power 340W 355W
Furmark Power 361W 422W

As expected, power and temperature both increase with FurMark with PowerTune at 300W. At this point FurMark is no longer constrained by PowerTune and our 6970 runs at 880MHz throughout the test. Overall our power consumption measured at the wall increased by 60W, while the core clock for FurMark is 46.6% faster. It was under this scenario that we also “uncapped” PowerTune for Metro, when we found that even though Metro was being throttled at times, the performance impact was impossibly small.

Meanwhile we found something interesting when running Crysis. Even though Crysis is not impacted by PowerTune, Crysis’ power consumption still crept up by 15W. Performance is exactly the same, and yet here we are with slightly higher power consumption. We don’t have a good explanation for this at this point – PowerTune only affects the core clock (and not the core voltage), and we never measured Crysis taking a hit at 250W or 300W, so we’re not sure just what is going on. However we’ve already established that FurMark is the only program realistically impacted by the 250W limit, so at stock clocks there’s little reason to increase the PowerTune limit.

This does bring up overclocking however. Due to the limited amount of time we had with the 6900 series we have not been able to do a serious overclocking investigation, but as clockspeed is a factor in the power equation, PowerTune is going to impact overclocking. You’re going to want to raise the PowerTune limit when overclocking, otherwise PowerTune is liable to bring your clocks right back down to keep power consumption below 250W. The good news for hardcore overclockers is that while AMD set a 20% limit on our reference cards, partners will be free to set their own tweaking limits – we’d expect high-end cards like the Gigabyte SOC, MSI Lightning, and Asus Matrix lines to all feature higher limits to keep PowerTune from throttling extreme overclocks.

Meanwhile there’s a second scenario AMD has thrown at us for PowerTune: tuning down. Although we generally live by the “more is better” mantra, there is some logic to this. Going back to our dynamic range example, by shrinking the dynamic power range power hogs at the top of the spectrum get pushed down, but thanks to AMD’s ability to use higher default core clocks, power consumption of low impact games and applications goes up. In essence power consumption gets just a bit worse because performance has improved.

Traditionally V-sync has been used as the preferred method of limiting power consumption by limiting a card’s performance, but V-sync introduces additional input lag and the potential for skipped frames when triple-buffering is not available, making it a suboptimal solution in some cases. Thus if you wanted to keep a card at a lower performance/power level for any given game/application but did not want to use V-sync, you were out of luck unless you wanted to start playing with core clocks and voltages manually. By being able to turn down the PowerTune limits however, you can now constrain power consumption and performance on a simpler basis.

As with the 300W PowerTune limit, we ran our power/temperature/noise tests with the 200W limit to see what the impact would be.

Radeon HD 6970: PowerTune Performance
PowerTune 250W PowerTune 200W
Crysis Temperature 78 71
Furmark Temperature 83 71
Crysis Power 340W 292W
Furmark Power 361W 292W

Right off the bat everything is lower. FurMark is now at 292W, and quite surprisingly Crysis is also at 292W. This plays off of the fact that most games don’t cause a card to approach its limit in the first place, so bringing the ceiling down will bring the power consumption of more power hungry games and applications down to the same power consumption levels as lesser games/applications.

Although not whisper quiet, our 6970 is definitely quieter at the 200W limit than the default 250W limit thanks to the lower power consumption. However the 200W limit also impacts practically every game and application we test, so performance is definitely going to go down for everything if you do reduce the PowerTune limit by the full 20%.

Radeon HD 6970: PowerTune Crysis Performance
PowerTune 250W PowerTune 200W
2560x1600 36.6 28
1920x1200 51.5 43.3
1680x1050 63.3 52

At 200W, you’re looking at around 75%-80% of the performance for Crysis. The exact value will depend on just how heavy of a load the specific game/application was in the first place.

PowerTune, Cont Another New Anti-Aliasing Mode: Enhanced Quality AA
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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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