AMD Radeon HD 6970 and HD 6950 Review

Author: Michael "SKYMTL" Hoenig
Date: December 14, 2010
Product Name: AMD Radeon HD 6970 / HD 6950
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PowerTune: Keeping Consumption in Check

One of the largest challenges GPU manufacturers have been smashing into as of late is the rapid increase in the power consumption of their higher-end ASICs. NVIDIA’s solution to cut consumption and TDP in their GTX 500-series has been a combination of input current monitoring and upgraded heatsinks as well as application detection. AMD meanwhile is taking a different path with their PowerTune technology which uses a complex set of current calculations to determine on-the-fly TDP levels. It can then adjust clock speeds once the card reaches a pre-determined maximum thermal design power level.

The entire point of PowerTune is to allow AMD to strike a delicate balance between power consumption, thermals and clock speeds. If such a middle-man didn’t exist, the clock speeds of Cayman series products would have been significantly lower since there would have been nothing to keep TDP in check.

A typical GPU will likely be used of any number of applications but its primary focus will usually be upon one thing: entertainment. While there are several synthetic benchmarks which cause a graphics card to consume copious amounts of power, most typical games will never even begin to approach these levels. As such, AMD is focusing their PowerTune technology upon scenarios which put unrealistic loads upon the GPU rather than games. Since most of us don’t sit around all day benchmarking with 3DMark, this is good news.

Unfortunately, depending on their rendering methods there may still be the odd game which will be caught up in the crossfire and have its performance capped but we will be tackling this potential issue in a later section. It is just important to remember that AMD has tuned this technology to deliver the best gaming performance while weeding out potential power viruses.

As AMD describes it, this new technology is simply used to contain power consumption in such a way that the actual TDP of a given product will in effect determine clock speeds. Instead of letting the card run amok for the few seconds of absolute peak consumption that will likely occur every now and then, PowerTune caps power draw through clock speed modification. After the peak periods are concluded, clock speeds along with performance will return to normal.

This may all sound like doom and gloom for overall performance but PowerTune is actually designed for a worst-case scenario rather than a typical usage pattern. The algorithm to determine implied power consumption is based upon an extremely high leakage ASIC operating with 45 degree inlet temperature. Remember that high temperatures increase power draw in transistors so this ensures products are not artificially capped in lower temperature scenarios. Since TDP is the determining factor here, if you keep your card cool within a well ventilated case you should in theory never see PowerTune kick in while gaming.

Even in one of those power sucking scenarios like the Perlin Noise test in 3DMark Vantage, the cards are able to maintain a constant framerate whilst fluctuating the core clock. Of course this does tend to decrease the overall peaks and valleys normally seen in benchmark sequences’ performance but in AMD’s thinking, this is better than seemingly random application detection kicking in.

One of the beauties of this technology is the control the end user has over it. Within the Catalyst Control Center’s Overdrive panel, there is now a Power Control Setting slider that allows PowerTune to add some overhead to its calculations. This could also improve overclocking since it allows the core to loosen its grip on TDP.

While the current PowerTune cap for the HD 6970 is 250W and the HD 6950 is 200W, this will allow for theoretical consumption limits of 300W and 240W respectively which could increase performance if one is running into rendering limitations. However, setting additional overhead does not guarantee games will perform any better since as we saw there are very few (if any) applications that will be limited by the already-lax limits AMD has instituted. It should also be mentioned that since PowerTune is considered an overclocking tool, its usage will not be covered by certain board partners’ warranties.

Consequently, AMD has also allowed for the tightening of containment as well. There may not be much value in this for a typical hardcore gamer but if performance is above that magical 60 FPS mark, lowering the PowerTune setting could still net perfectly acceptable framerates coupled with lower power consumption and temperatures.

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