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.
MSI R7970 Lightning Stock BIOS
MSI R7970 Lightning OC BIOS
GeForce GTX 580 OC
At idle we see that the MSI card actually sits above the level we would expect for a 7970, well by 6w or so anyway which takes it a little closer to the GTX 580 level with all three results similar for temperatures. Interestingly the "stock" bios on the MSI card is drawing more power at idle.
Moving to load things become a little more as expected with the stock BIOS using less power than load and the MSI card, even overclocked, still running on significantly lower watts than the GTX 580. Temperatures remain the same on the MSI card regardless of the BIOS with the fan speed varying a little to cover the OC settings.
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.
Overclocking on the MSI 7970 is a simple process; we open our driver control panel and head into the Overdrive section or use MSI's own Afterburner utility which offers more in-depth monitoring and voltage tweaking. We simply begin moving the sliders to our desired speed and it is as easy as that to overclock.
Stock 3D Mark
On our sample we were able to achieve were 1265MHz on the core and 1505 MHz on memory with the overclocked BIOS. That is the highest core overclock we have seen on a 7970 by some way and the end result is the performance increases shown throughout this review.