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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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  • AnnihilatorX - Thursday, December 16, 2010 - link

    I disagree with you rarson

    This is what sets Anandtech apart, it has quality over quantity.
    Anandtech is the ONLY review site which offers me comprehensive information on the architecture, with helpful notes on the expected future gaming performance. It mention AMD intended the 69xx to run on 35nm, and made sacrifices. If you go to Guru3D''s review, the editor in the conclusion stated that he doesn't know why the performance lacks the wow factor. Anandtech answered that question with the process node.

    If you want to read reviews only, go onto google and search for 6850 review, or go to DailyTech's daily recent hardware review post, you can find over 15 plain reviews. Even easier, just use the Quick Navigation menu or the Table of Content in the freaking first page of article. This laziness does not entrice sypathy.
    Reply
  • Quidam67 - Thursday, December 16, 2010 - link

    Rarson's comments may have been a little condescending in their tone, but I think the critism was actually constructive in nature.

    You can argue the toss about whether the architecture should be in a separate article or not, but personally speaking, I actually would prefer it was broken out. I mean, for those who are interested, simply provide a hyper-link, that way everyone gets what they want.

    In my view, a review is a review and an analysis on architecture can compliment that review but should not actually a part of the review itself. A number of other sites follow this formula, and provide both, but don't merge them together as one super-article, and there are other benefits to this if you read on.

    The issue of spelling anf grammer is trivial, but in fact could be symptomatic of a more serious problem, such as the sheer volume of work Ryan has to perform in the time-frame provided, and the level of QA being squeesed in with it. Given the nature of NDA's, perhaps it might take the pressure off if the review did come first, and the architecture second, so the time-pressures weren't quite so restrictive.

    Lastly, employing a professional proof-reader is hardly an insult to the original author. It's no different than being a software engineer (which I am) and being backed up by a team of quality test analysts. It certainly makes you sleep better when stuff goes into production. Why should Ryan shoulder all the responsibility?
    Reply
  • silverblue - Thursday, December 16, 2010 - link

    I do hope you're joking. :) (can't tell at this early time) Reply
  • Arnulf - Thursday, December 16, 2010 - link

    "... unlike Turbo which is a positive feedback mechanism."

    Turbo is a negative feedback mechanism. If it was a positive feedback mechanism (= a consequence of an action resulting in further action in same direction) the CPU would probably burn up almost instantly after Turbo triggered as its clock would increase indefinitely, ever more following each increase, the higher the temperature, the higher the frequency. This is not how Turbo works.

    Negative feedback mechanism is a result of an action resulting in reaction (= action in the opposite direction). In the case of CPUs and Turbo it's this to temperature reaction that keeps CPU frequency under control. The higher the temperature, the lower the frequency. This is how Turbo and PowerTune work.

    The fact that Turbo starts at lower frequency and ramps it up and that PowerTune starts at higher frequency and brings it down has no bearing on whether the mechanism of control is called "positive" or "negative" feedback.

    Considering your fondness for Wikipedia (as displayed by the reference in the article) you might want to check out these:

    http://en.wikipedia.org/wiki/Negative_feedback
    http://en.wikipedia.org/wiki/Positive_feedback

    and more specifically:

    http://en.wikipedia.org/wiki/Negative_feedback#Con...
    Reply
  • Ryan Smith - Thursday, December 16, 2010 - link

    Hi Arnulf;

    Fundamentally you're right, so I won't knock you. I guess you could say I'm going for a very loose interpretation there. The point I'm trying to get across is that Turbo provides a performance floor, while PowerTune is a performance ceiling. People like getting extra performance for "free" more than they like "losing" performance. Hence one experience is positive and one is negative.

    I think in retrospect I should have used positive/negative reinforcement instead of feedback.
    Reply
  • Soda - Thursday, December 16, 2010 - link

    Anyone noticed that the edge missing og the boards 8-pin power connector ?

    Apparently the AMD made a mistake in the reference design of the board and didn't calculating the space needed by the cooler.

    If you look closely on the power connector in http://images.anandtech.com/doci/4061/6970Open.jpg you'll notice the missing edge.

    For a full story on the matter you can go to http://www.hardwareonline.dk/nyheder.aspx?nid=1060...
    For the english speaking people I suggest the googlish version here http://translate.google.com/translate?hl=da&sl...

    There are some pictures to backup the claim the mistake made AMD here.

    Though it haven't been confirmed by AMD if this is only a mistake on the review boards or all cards of the 69xx series.
    Reply
  • versesuvius - Thursday, December 16, 2010 - link

    I have a 3870, on a 17 inch monitor, and everything is fine as long as games go. The hard disk gets in the way sometimes, but that is just about it. All the games run fine. No problem at all. Oh, there's more: They run better on the lousy XBOX. Why the new GPU then? Giant monitors? Three of them? Six of them? (The most fun I had on Anandtech was looking at pictures of AT people trying to stabilize them on a wall). Oh, the "Compute GPU"? Wouldn't that fit on a small PCI card, and act like the old 486 coprecessor, for those who have some use for it? Or is it just a silly excuse for not doing much at all, or rather not giving much to the customers, and still charge the same? The "High End"! In an ideal world the prices of things go down, and more and more people can afford them. That lovely capitalist idea was turned on its head, sometime in the eighties of the last century, and instead the notion of value was reinvented. You get more value, for the same price. You still have to pay $400 for your graphic card, even though you do not need the "Compute GPU", and you do not need the aliased superduper antialiasing that nobody yet knows how to achieve in software. Can we have a cheap 4870? No that is discontinued. The 58 series? Discontinued. There are hundreds of thousands or to be sure, millions of people who will pay 50 dollars for one. All ATI or Nvidia need to do is to fine tune the drivers and reduce power consumption. Then again, that must be another "High End" story. In fact the only tale that is being told and retold is "High End"s and "Fool"s, (i.e. "We can do whatever we want with the money that you don't have".) Until better, saner times. For now, long live the console. I am going to buy one, instead of this stupid monstrosity and its equally stupid competitive monstrosity. Cheaper, and gets the job done in more than one way.

    End of Rant.
    God Bless.
    Reply
  • Necc - Thursday, December 16, 2010 - link

    So True. Reply
  • Ananke - Thursday, December 16, 2010 - link

    Agree. I have 5850 and it does work fine, and I got it on day one at huge discount, but still - it is kind of worthless. Our entertainment comes more exclusively from consoles, and I discrete high end card that commands above $100 price tag is worthless. It is nice touch, but I have no application for it in everyday life, and several months later is already outdated or discontinued.

    My guess, integrated in the CPU graphics will take over, and the mass market discrete cards will have the fate of the dinosaurs very soon.
    Reply
  • Quidam67 - Thursday, December 16, 2010 - link

    Wonderfully subversive commentary. Loved it.

    Still, the thing I like about the High end (I'll never buy it until my Mortgage is done with) is that it filters down to the middle/low end.

    Yes, lots of discontinued product lines but for example, I thought the HD5770 was a fantastic product. Gave ample performance for maintstream gamers in a small form-factor (you can even get it in single slot) with low heat and power requirements meaning it was a true drop-in upgrade to your existing rig, with a practical upgrade path to Crossfire X.

    As for the xbox, that hardware is so outdated now that even the magic of software optimisation (a seemingly lost art in the world of PC's) cannot disguise the fact that new games are not going to look any better, or run any faster, than those that came out at launch. Was watching GT5 in demo the other day and with all the hype about how realistic it looks (and plays) I really couldn't get past the massive amount of Jaggies on screen. Also, very limited damage modelling, and in my view that's a nod towards hardware limitations rather than a game-design consideration.
    Reply

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