For this test we monitored each of the rails of the PSU under various loads, which represent different power-hungry PC configurations. We took voltage measurements for 150W, 300W 450 W, 600W and finally 750W loads.

The current ATX specifications allow for the following fluctuations in voltage outputs:

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

An oscilloscope was also used to examining the voltage ripple on the rails using the proper capacitors in place to filter noise. This measures how clean the power delivery really is for the tested power supply. The ATX specifications' requirement for ripple is 120 mV for 12V and 50mV for the rest outputs. 

In the crossload tests, we firstly stressed the two minor rails (5V and 3.3V) with a high load while the load at +12V was only 2A. For the second crossload test we applied the maximum load that the +12V rail could handle while the load on the minor rails was very low.

The results is illustrated below:

As you see below, the voltage deviations as well as ripple for all the outputs were well within the acceptable limits.

Voltage regulation at +12V is good, although we would expect a better behavior of the minor rails.

Efficiency was also high for all the loads and of course, higher than 80% in order to comply with the 80 Plus standard.

Regarding noise levels, we measured any audible sound from a 1m distance from the PSU. The fan was silent until the 300W loads. A low 34dB(a) was measured after the 450W point and reached the 34.8dB(A) under full load.