Power, Temps, Noise and Overclocking
As with the Radeon 6900 series and GTX 500 series the 7800 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.
Starting with the idle readings we see that the Sapphire 7850 OC sits around 2w less in power use than a reference 7870 with the older Radeon and Geforce over 130w. Temperatures are close between our 560 Ti and 7850 at idle however when we move to load the Radeon has a temperature which is 13°C lower while requiring 100w less to achieve its performance.
Noise levels are also very good with Sapphire clearly leaning towards lower RPM for their fan profile as this video shows.
Sticking with the power and noise theme for a moment one of the key 7000 series features which was covered in our original reviews 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 Sapphire 7800 series is a simple process; we open their free TriXX utility or the AMD control panel and head into the appropriate section. In there we can maximise the clock setting by moving the sliders to our desired speed.
In this test the Sapphire card is able to run at the maximum speed available when overclocking, 1050/1450MHz which gives us an increase of around 600 points.