Energy consumptionWe measured the energy consumption of the graphics card on its own. We took these readings at idle, in 3D Mark 06 and Furmark. Note that we use a version of Furmark that isn’t detected by the stress test energy consumption limitation mechanism put into place by NVIDIA in the drivers for the GeForce GTX 500s.
While energy consumption at idle is the same as on the Radeon HD 5970, and pretty reasonable for a card of this calibre, it explodes in load. Strangely, PowerTune seems to function differently in the two bios’, something we imagine is linked to GPU temperature. The higher the temperature gets, the more current leakage there is, which has a direct effect on energy consumption. We can therefore imagine that AMD hasn’t fully taken this higher temperature into account and hasn’t been particularly conservative in defining the activity to energy consumption estimation ratios in the 450 watts mode.
This means there’s more of a margin, either for overclocking the GPU or in situations of extreme load as is the case with Furmark. Thus in 375W mode, we measured the GPU clock as varying from 535 to 830 MHz, with an average of 560 MHz, while in 450W mode, the GPU clock oscillated between 670 and 880 MHz, with an average of 765 MHz. The gain in performance in Furmark was therefore a little more than 20%! It should be noted that PowerTune acts in an extreme way here, because of the load of the test in Furmark. Games don’t push the GPU as hard in terms of energy consumption and then PowerTune hardly kicks in at all.
Note that in spite of its extreme energy consumption, the Radeon HD 6990 does not exceed the maximum consumption defined for the PCI Express bus. While the standard authorises cards to draw 5.5A from 12V, the maximum level observed with the 450W bios was 5.32A. There’s therefore no risk of damaging your motherboard in the way that there is with the GeForce GTX 480 and 580.
To observe the noise levels produced by the card, we put it in an Antec Sonata 3 casing and measured noise at idle and in load. We placed the sonometer 60 cm from the casing.
Although the Radeon HD 6990 is discreet in idle, in load it breaks the record previously set by the GeForce GTX 480 in SLI and scores over 59 dB. Here the fan is running at full speed (4900 RPM).
Note that in 375W mode, noise levels vary between 52.8 dB and 59.4 dB. The fan runs at 3600 RPM at first and then, as the temperature goes up, accellerates progressively to 4900 RPM, with temperatures dropping after several tens of seconds and then the fan gradually dropping back down to 3600 RPM before the temperature starts to go up again and the cycle starts again. We therefore imagine that if your casing is well cooled, you should be able to keep the fan running at lower speeds. In any case, it’s a long way from being quiet!