NVIDIA GPU Boost makes it difficult to measure accurately
The GPU Boost procedure allows the core clock to be set automatically, which certainly gives rise to tricks.
The IT website Hardware.fr has once again begun an in-depth analysis. The focus is now on NVIDIA GPU Boost. To keep performance at an ideal level, Kepler chips also take into account graphics processor load, power consumption, memory usage, and current temperature, and increase the pace accordingly. According to the official documentation, the clock increase takes place in 100 ms, so users do not notice anything about it. In practice, this means that the GK104 operates at a base base speed of 1006 MHz (core base), but after evaluating the former factors, the chip can boost this up to 1110 MHz (core boost). NVIDIA calculates that the average result achieved by the GPU Boost is 1058 MHz. So far, this is not considered a novelty.
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Based on Damien Triolet's analysis, the clock signal is increased per unit. One unit means exactly 13 MHz, i.e. the speed can be increased by a total of 104 MHz. The GeForce GTX 680 sent to Hardware.fr was indeed able to achieve the 8-unit boost, reaching an outstanding 1,10 GHz. The problems started when the magazine received a copy from a shop, which "only" reached 1084 MHz (6 units), but a situation can also occur when this standard cannot be exceeded. All indications are that the GeForce GTX 680 cards delivered to the test sites were selected copies capable of slightly higher clock speeds than the retail products. It is worth noting that even this small difference causes an average difference of 1,5%, which in some cases can reach 5%. As stated above, NVIDIA guarantees an average value of 1058 MHz, so there is no reason to complain, but due to the former factor, it may happen that the performance achieved by the test pages will be unattainable for an average version.
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The above information is confirmed by the measurements of the German HT4u and even provides an interesting additive. Since GPU Boost is (also) a function of temperature, you shouldn't be surprised at all if the clock rise decreases over time. Based on the measurements, with a little luck, the operating frequency of 1,10 GHz is indeed available, but after a few minutes the chip can no longer keep up with this pace. The results also show that during the Anno 2070, a less successful model can withstand an increase of just 1-2 units, which means a speed of only 1019-1033 MHz - although this game would specifically thank the high clock speed.
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After observing the temperature, the explanation really emerges clearly. As the GPU enters an increasingly warmer range, it needs to gradually regain momentum. For understandable reasons, when approaching the critical temperature point - 98 degrees is a kind of safety margin - 1058 MHz is a dream. Low operating temperatures (50-60 degrees) are especially advantageous for Kepler-based cards, although it is a GeForce GTX 680 or a GTX 690 is not an easy task for users. The other factor is luck, but we can no longer influence it by scientific methods.
Overall, there were no big surprises. Unfortunately, NVIDIA's official documentation does not discuss the service in detail, so it took some time to explore it. Since GPU Boost can also be thought of as a kind of overdrive, it’s not unexpected that two cards perform differently. Nor is it a recent phenomenon for companies to send sorted copies to larger test pages. In this case, NVIDIA has more room to maneuver than usual, as it does not matter whether a card operates between 1019-1033 or 1097-1110 Mhz. The former during each game can result in the strongest title of a GPU controller shaking against the AMD Radeon HD 7970.
Source: hardware.fr, ht4u.net
