Power, Temps, Noise and Overclocking
As with the Radeon 6900 series and GTX 500 series the 7900 series performs power management in a different way to older cards so we have changed the way we test power and temperature levels in our reviews. For idle power we list the full system use at the wall after sitting at the desktop with no activity for 5 minutes. Load power is the highest reading we saw for the full system when testing during this review. Temperatures are taken in the same way. Noise levels are taken after a period of prolonged gaming in a scenario which applied maximum load to the GPU.
For the comparison with our overclocked GeForce card the Sapphire model does well at idle, offering similar temperatures but significantly better power use. At load that changes a little with our Zotac OC model offering a little better on the temperature front but Sapphire excel on power use, knocking 60w or so off the GeForce reading.
Looking next to the differences between Sapphires two BIOS profiles we see that at idle the two settings are near identical. When we apply load to the card this changes though and the second profile draws more power when peaking, though the temperature stays the same. With the card working harder, or faster really the cooler has to do more to maintain this 72c and so the noise level increases a little, though this is still a quiet card even then.
Sticking with the power and noise theme for a moment one of the key 7970 features which was covered in our original review is the advanced power management which has been implemented in Crossfire. In that mode AMD are able to send the second card to an ultra-low power state when idle and as shown below this means turning the GPU and memory to 0MHz.
As an added bonus to the second (or additional) cards minimal power use the driver also shuts down the fan turning the card into a silent model. For completeness before we look at overclocking, also included above is a noise level video for the Crossfire configuration at load. Sapphire fully support this technology on their 7970s.
On our sample we were able to achieve 1230MHz on the core and 1515MHz on memory with BIOS 2. This is higher than what we achieved on the original reference card and therefore the overall 3DMark score, and performance increases also.