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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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  • DoktorSleepless - Wednesday, December 15, 2010 - link

    What benchmark or game is used to measure noise? Reply
  • Hrel - Wednesday, December 15, 2010 - link

    I'm not 100% but I believe they test it under Crysis. It was either that or a benchmark that put full load on the system. It was in an article in last year or 2, I've been reading so long it's all starting to mesh together; chronologically. But suffice it to say it stresses the system. Reply
  • Hrel - Wednesday, December 15, 2010 - link

    It's furmark, it's in the article. Reply
  • Adul - Wednesday, December 15, 2010 - link

    nice Christmas gift from the GF :D Reply
  • AstroGuardian - Wednesday, December 15, 2010 - link

    I saw my GF buying a couple of those. One is supposed to be for me and she doesn't play games...... WTF? Reply
  • MeanBruce - Wednesday, December 15, 2010 - link

    Wow, you are getting a couple of 6950s? All I am getting from my 22yo gf is a couple of size F yammos lying on a long narrow torso, and a single ASUS 6850. Don't know which I like better, hmmmmm. Wednesday morning comic relief. Reply
  • Adul - Wednesday, December 15, 2010 - link

    damn sounds good to me :) enjoy both ;) Reply
  • SirGCal - Wednesday, December 15, 2010 - link

    I'm happy to see these power values! I did expect a bit more performance but once I get one, I'll benchmark it myself. By then the drivers will likely have changed the situation. Now to get Santa my wish list... :-) If it was only that easy... Reply
  • mac2j - Wednesday, December 15, 2010 - link

    One of the most impressive elements here is that you can get 2x6950 for ~$100 more than a single 580. That's some incredible performance for $600 which is not unheard of as the price point for a top single-slot card.

    Second... the scaling of the 6950 combined with the somwhat lower power consumption relative to the 570 bodes well for AMD with the 6990. My guess is they can deliver a top performing dual-GPU card with under a 425-watt TDP .... the 570 is a great single chip performer but getting it into a dual-gpu card under 450-500w is going to be a real challenge.

    Anyway exciting stuff all-around - there will be a lot of heavy-hitting GPU options available for really very fair prices....
    Reply
  • StormyParis - Wednesday, December 15, 2010 - link

    It's nice to have all current cards listed, and helps determine which one to buy. My question, and the one people ask me, is rather "is it worth upgrading now". Which depends on a lot of things (CPU, RAM...), but, above all, on comparative perf between current cards and cards 1-2-3 generations out. I currently use a 4850. How much faster would a 6850 or 6950 be ? Reply

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