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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  • anactoraaron - Wednesday, December 15, 2010 - link

    I would like to thank Ryan for the article that makes me forget the "OC card in the review" debacle. Fantastic in depth review with no real slant to team green or red. Critics go elsewhere please. Reply
  • Hrel - Wednesday, December 15, 2010 - link

    When are you guys gonna put all these cards in bench? Some of them have been out for a relatively long time now and they're still not in bench. Please put them in there. Reply
  • ajlueke - Wednesday, December 15, 2010 - link

    I agree with most of the conclusions I have read here. If you already own a 5800 series card, there isn't really enough here to warrant an upgrade. Some improved features and slightly improved FPS in games doesn't quite give the same upgrade incentive as the 5870 did compared a 4870.
    There are some cool things with the 6900 and 6800 series. Looking at the performance in games, the 6970 and even the 6870 seemed to get much closer to 2X performance when placed in crossfire as compared to 5800 series cards. That is a pretty interesting development. All in all, a good upgrade if you didn't buy a card last generation. If you did, it seems the wait is on for the 28 nm version of the GPU.
    Reply
  • Belard - Wednesday, December 15, 2010 - link

    NO!

    The 800 cards were the HIGH end models since the 3000 series and worked well through to the 5000 series with the 5970 being the "odd one" since the "X2" made more sense like the 4850X2.

    It also allows for a "x900" series if needed.

    AMD needs to NOT COPY Nvidia's naming games... did they hire someone from Nvidia? Even the GeForce 580/570 still belong to the 400 series since its the same tech. SHould have been named 490 and the 475... But hey, in 12 months, Nvidia will be up to the 700 series. Hey, Google Chrome is version 8.0 and its been on the market for about 2 years! WTF?!

    What was their excuse again? Oh, to not create confusion with the 5700 series? So they frack up the whole model names for a mid-range card? The 6800's should have been 6700s, simple as that. Yes, there will be some people who will accidentally downgrade.

    What the new 6000 series has going for AMD is that they are somewhat cheaper and easily cost less to make than the 5000s and what Nvidia makes.

    In the end, the 6000 series is the first dumb-thing AMD has done since the 2000 series, but nowhere near as bad.
    Reply
  • MS - Wednesday, December 15, 2010 - link

    In terms of effienct usage of space though AMD is doing quite well; ... should be efficient

    Nice article so far,

    Regards,
    Michael
    Reply
  • nitrousoxide - Wednesday, December 15, 2010 - link

    The power connector on the left (8-pin of 6970 and 6-pin of 6950) has a corner (bottom left corner) cut down, that's because the cooler doesn't fit with the PCB design, if you install it with force the power connector would get stuck. So the delay of 6900 Series could be due to this issue, AMD needs one month to 'manually polish' all power connectors of the stock-cards in order to go with the cooler. Well, just a joke, but this surely reflects how poorly AMD organizes the whole design and manufacture process :) Reply
  • nitrousoxide - Wednesday, December 15, 2010 - link

    you can find this out here :)
    hiphotos. baidu. com/coreavc/pic/item/70f48d81ffe07cf26d811957. jpg
    Reply
  • nitrousoxide - Wednesday, December 15, 2010 - link

    AMD promises that every one will get a unique 6970 or 6950, different from any other card on the planet :) Reply
  • GummiRaccoon - Wednesday, December 15, 2010 - link

    The performance of these cards is much better with 10.12, why didn't you test it with that? Reply
  • Ryan Smith - Wednesday, December 15, 2010 - link

    10.12 does not support the 6900 series.

    8.79.6.2RC2, dated December 7th, were the absolute latest drivers for the 6900 series at the time of publication.
    Reply

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