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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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  • fausto412 - Wednesday, December 15, 2010 - link

    6970 just 4 to 6 fps faster in Bad Company 2 than my 5870? WTF!

    not worth the upgrade. what a lame ass successor.
    Reply
  • Kibbles - Wednesday, December 15, 2010 - link

    It's 7% faster at 1920 and 9% faster at 2560. BC2 obviously doesn't need the extra GPU power at 1680.

    I wouldn't call it weak, but this card certainly isn't the clear winner that the 5870 was.
    Reply
  • fausto412 - Wednesday, December 15, 2010 - link

    its weak if i was expecting a response to the gtx580 to upgrade to.

    may as well stay with my 5870.
    Reply
  • ClownPuncher - Wednesday, December 15, 2010 - link

    For now... But who really bases their purchase on one game anymore? It looks like 10.12 or 11.1 drivers will help performance a good amount. Reply
  • fausto412 - Wednesday, December 15, 2010 - link

    I base my performance on 1 game...because it is a very taxing game and my #1 game right now. Reply
  • MeanBruce - Wednesday, December 15, 2010 - link

    Yup, dude I heard the AMD 7000 series might make an early appearance next July, with the die shrink @28nm you might want to wait and pick up a 7970! Reply
  • fausto412 - Wednesday, December 15, 2010 - link

    that's what i'm considering now. need to upgrade for 30% more performance than 5870 for it to make sense. Reply
  • Stuka87 - Wednesday, December 15, 2010 - link

    The game is CPU limited at lower resolutions. BC2 is known for being more CPU bound than GPU bound.

    But I was hoping for a larger jump over the previous cards :/
    Reply
  • fausto412 - Wednesday, December 15, 2010 - link

    I understand BFBC2 is more cpu bound. But in this testing Anandtech did they use a TOP TOP TOP of the line cpu so that rules that out as a bottleneck. Reply
  • Belard - Wednesday, December 15, 2010 - link

    Yeah... at least the model numbers didn't make things confusing!

    In some benchmarks, the 6950 is faster than your 5870... but it would have made far more sense to call these 6850/6870 or even 6830/6850..

    AMD screwed up with the new names...
    Reply

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