Our testing methodology for testing Power Supply Units is limited to the multi-meter to show each rails performance due to us not having access to an ATE load tester. We are making plans to invest in equipment as we were directed by Cooler Master when Simon visited their test labs in June 2010.

Although this does constrain us slightly we can still monitor fluctuations on the rails and give the unit a good assessment when we feature it in one of our builds. The way the testing will run is simple, voltages will be observed at idle wattage and then a single GPU will be installed within the system and a combination of OCCT and MSI Kombustor will be executed to provide simulation with just 1 GPU. This will be run for 10 minutes. We will also be adding in another GPU and configuring SLI in order to generate as much power consumption as possible. The CPU will also be overclocked to maximise power consumption and strain. This should give us a good indication of how the HX850 will perform under gaming stresses and beyond.

System Components


As I mentioned there is no ATE load tester available so generating as much power as possible is key to observing the fluctuations on the rails.

For voltage tolerance levels, ATX specify that a 5% variable fluctuation is acceptable. (Form Factors - ATX Specification PDF - Page 10). So what this means is:

3.3V Rail - 3.135V - 3.465V acceptable
5V Rail - 4.75V – 5.25V acceptable
12V Rail - 11.4V – 12.6V acceptable

Idle test - The system settles in windows without any applications or stressing. 1 GPU (165W)
Single GPU - OCCT/MSI Kombustor run for 10 minutes (382W)
Dual GPU - OCCT/MSI Kombustor run for 10 minutes (683W)