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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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  • versesuvius - Friday, December 17, 2010 - link

    Ananke,

    I am not very knowledgeable about this, but I don't think a modern GPU can fit inside a CPU for now. A better idea would be a console on a card. The motherboards on the consoles are not much bigger than the large graphic cards of today. A console card for $100 would be great. I am sure that there is no technical obstacles that the average electronic wizard cannot overcome, doing that.

    Sure, there is a use for everything. I can imagine that every single human being on earth can find a use for a Ferrari, but the point is that even those who do have it, do not use it as often as their other car, (Toyota, VW or whatever). In fact, there is rarely a Ferrari that has more than 20,000 km on it, and even that is put on it by successive owners, not one. The average total an ordinary person can stand a Ferrari is 5000 KM. (Disclaimer: I do not have one. I only read something to that effect somewhere). Having said that, I do have a sense of the "need for speed". I can remember sitting in front of the university's 80286 waiting for the FE program to spit out the results, one node at a time, click, click, ... . You have millions of polygons, we can have billions of mesh nodes, and that even does not even begin to model a running faucet. How's that for the need for speed. I do appreciate the current speeds. However, the CPU deal was and is a straight one. The graphic card deals, today, are not. To be clear, the "and" in "High End"s and "Fool"s is an inclusive one. "Someone will pay for it", was also initiated in the eighties of the last century. By the way, the big question "can it play crysis", will no longer be. Crysis 2 is coming to the consoles.
    Reply
  • Quidam67 - Friday, December 17, 2010 - link

    "But can it play Crysis" should be in the Urban dictionary as a satirical reference on graphics code that combines two potent attributes: 1) is way ahead of its time in terms of what current hardware can support 2) is so badly written and optimised that even hardware that should be able to run it still can't.

    In 1000 years time when Organic Graphics cards that you can plug into your head still can't run it smoothly @2560*1600 60fps they will realise the joke was on us and that the code itself was written to run more and more needless loops in order to overwhelm any amount of compute-resource thrown at it.
    Reply
  • Iketh - Friday, December 24, 2010 - link

    LOL Reply
  • marc1000 - Friday, December 17, 2010 - link

    I swear I've read ALL the comments to see if anyone already pointed it... but no one did.

    I feel a bit disappointed with this launch too (I have a 5770 and wanted to get 6950 but was wanting a bigger increase %-wise). But one thing interesting it the number of Stream Processors in the new gpus. By the "pure processor" count this number decreased from 1600 SPs on 5870 to 1536 SPs on 6970. But the size of the VLIW processors changed too. It was 5 SPs on 5870 and now is 4 SPs.

    So we have:
    hd5870 = 1600 SPs / 5 = 320 "processors"
    hd6970 = 1536 SPs / 4 = 384 "processors"

    if we take that 384 and multiply by 5, we would have 1920 SPs on the new generation (on par with many rumors). this is 20% more shaders. and considering AMD is saying that the new VLIW4 is 10% faster than VLIW5 we should have more than 20% increase in all situations. but this is only true in the minority of tests (like crysis at 2560x1660 where it is 24%, but in the same game at 1680x1050 the increase is only 16%). and at the same time the minimun FPS got better, yet in another games the difference is smaller.

    but then again, I was expecting a little more. I believe the 6950 will be a worthy upgrade to me, but the expectations were so high that too much people ended a little disappointed... myself included.
    Reply
  • Sunburn74 - Tuesday, December 28, 2010 - link

    Well... at least they delivered on time and didn't make you wait 6 more months to simply deliver an equivalent, if not considerably worse, product. Reply
  • Mr Perfect - Friday, December 17, 2010 - link

    Yes, the minimums are appreciated when they're included.

    It would be even better if the framerates was displayed as a line graph instead of a bar graph. That way readers could tell if an average consisted of a lot of high peaks and low valleys, or really was a nice smooth experience all the way through. Some other review sites use linegraphs and while I visit Anandtech for it's timeliness, professionalism, industry insight and community involvement, I go to the other sites for the actual performance numbers.
    Reply
  • Quidam67 - Friday, December 17, 2010 - link

    There is further rationale for splitting the article. Lets say someone is googling "HD 6970 architecture" perhaps they will pick up this review, or perhaps they won't, but either way, if they see that it is actually a review on the cards, they might be inclined to bypass it in favour of a more focused piece.

    And again, there is no reason why the Architecture Article can't provide a hyperlink to the review, if the reader then decides they want to see how that architecture translates into performance on the current generation of cards supporting it.

    I really hope AT are reading this and giving it some consideration. As you say, they are a great sight and no one is disputing that, but it's not a religion, so you should be allowed to question it without being accused of blasphemy :O)
    Reply
  • dustcrusher - Friday, December 17, 2010 - link

    It really comes down to how important the mainstream market is. If they are a large enough segment of the market, one company using a simple, easy-to-grasp naming convention would likely grab some market share. Make it easy to buy your product and at least some people will be more likely to do so.

    If not, then it's fun to talk about but not terribly important. Tech-savvy folk will buy whatever meets their needs price/performance-wise after doing research, even if a card is named the Transylvania 6-9000 or the Wankermeister GTFO. Eager to please tech-naive folk are going to buy the largest model number they can get with the money they have, because "larger model numbers = bigger/better equipment" is a long-established consumer shorthand.

    I have a half-baked idea for a model numbering system that's based around the key specs of the card- it's a 5 digit system where the first digit is the hardware platform ID (like what we have now, mostly) and the other four would represent combinations of other specs (one digit could be the lowest memory clock speed and bus width would be 1, the next lowest memory clock speed and lowest bus width would be 2, etc).

    No idea if this could actually be implemented- there are probably too many variables with GPU/memory clock speeds, among other things.
    Reply
  • Shinobi_III - Saturday, December 18, 2010 - link

    If you ever saw Nvidia 4xAA in action, you know it's not as smooth as the radeon implementation (especially in motion) and z-buffer miscalculations has always been a nvidia feature.

    Go up a hill in Fallout New Vegas and look at Vegas in the horizon, with Nvidia cards it always looks like a disco due to meshes overlapping. Now do the same on Radeon.
    Reply
  • TheUsual - Saturday, December 18, 2010 - link

    Right now, Newegg has a 6870 for $200 after rebate. Two of these makes for an awesome value at $400. The top tier of cards doesn't give a corresponding increase in performance for the extra cost. Two 6950s costs 50% more but does not give you 50% more FPS. Two GTX 460 1GBs is also a great bang for the buck at $300.

    Neither of these lets you do triple SLI/XFIRE however. That would be what would be paying extra for.

    My hope is that the price will drop on the 6950 by around February. By then the GTX 560 should be out and might drive prices down some. The benchmarks could change some with Sandy Bridge too, if they are currently CPU bound.
    Reply

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