Here, we show the stability of the various power rails when the system is at idle and under load. When reading these charts, keep in mind that the closer to the exact number, the better. But also nearly as important is the difference between the rails. The less a rail changes between idle and load, the more stable the rail.
When evaluating the 3.3V rail, none of the PSUs stand out as poor performers. All of the units are very close to the target of 3.3 volts. The only PSU I would like to single out is the Antec 550W. Notice how the rails didn’t budge at all between idle and load, and they are very close to being exactly 3.3V!
As can be seen by the chart, the 5V rail is not one that fluctuates a lot. With that said, we can’t ignore that the AeroCool 620W is a little low compared to the other units, even at idle.
Here we see the AeroCool again very low on the 12V1 rail. But we also see the Ultra 550W drop dramatically when under load. All the other units seems to be rather stable at idle and load.
The 12V2 chart follows the same trend that the 12V1 chart does by showing the AeroCool voltage way down, and a big drop under load for the Ultra 550W. These are definitely two PSUs to be careful not to overload.
Four of the PSUs tested had more than two 12V rails. So for those units we tested the voltages at the graphics cards. All four of these power supplies provided ample volts to the graphics cards during testing.
After evaluating all of the charts on this page, we need to make a note that the AeroCool 620W and the Ultra 550W are two PSU’s to be causious of when choosing your next power supply. But make sure you read the conclusion as we point out any other important points we discovered during testing.