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 usually another GPU would be added to the system in order to generate more power draw but since this unit is 550W there is no need to do this. 1 GPU generates around 450W whilst adding another and the total usage exceeds 750W.

To add further power draw the CPU will be overclocked to maximise power consumption and strain. This should give us a good indication of how the OCZ ZT 500W will perform under gaming stresses and beyond. This is a good representation of real-world analysis.

System Components
CPU Intel Core i7 2500K (with OC 4.5GHz)
Motherboard ASUS P8P67
Graphics NVIDIA GTX 480
Memory 8GB Kingston HyperX 1600MHz CL9
HDD 2 x Samsung Spinpoint 500GB SATA-II
PSU OCZ ZT 550W

We all know how Fermi is notorious for its big power draw! 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 (215W)
Single GPU - OCCT/MSI Kombustor run for 10 minutes (422W)



The ZT 550W does an exceptional job throughout the voltage variance testing, all of the rails – 3.3V, 5V and 12V remain in the realm of ‘acceptable’ according to the ATX standards.

At 76% load the 140mm Yate Loon inside did generate unwanted noise levels.