Overall Voltage Characteristics

We compared the COUGAR PowerX 550W PSU against the Mushkin HP-580AP PSU. In all PSUs, the power rails must maintain their voltages to within 5% under the ATX12V specifications.

As you can see, while both PSUs met specifications, but the COUGAR PowerX 550W PSU definitely does a better job at keeping it closer to the desired voltage. The Mushkin PSU tends to be on the high side.

Voltages Under Load

We then ran a short stress test using a 3D game (Bioshock Infinite) - starting it up, running a short loop, and then quitting the game - to see how the PSUs handle the extra load. To further increase the load, we pre-loaded the testbed using extra hard disk drives, namely the 1 TB Western Digital VelociRaptor, the 4 TB Western Digital RE, the 3 TB Western Digital Green G2 (WD30EZRX), and the 3 TB Western Digital Red (WD30EFRX).

+12V Line (12V₁)

This power line is used to power the motors of peripheral components like the hard disk drives, PCI Express graphics cards, DVD writers, floppy drives, etc. Incidentally, the chart was adjusted to show you the minimum and maximum limits under the ATX12V specifications, so as long as the voltage lines remain within the chart, they are within specifications.

Both PSUs register a slight increase in voltage during heavier loads, with the Mushkin PSU on the high side.

+12V ATX Line (12V₂)

This power line powers the motherboard through the 4-pin ATX power connector. Again, the chart was adjusted to show you the minimum and maximum limits under the ATX12V specifications. As long as the voltage lines remain within the chart, they are within specifications.

Both PSUs exhibited tighter voltages, with the COUGAR PowerX 550W PSU doing slightly better than the Mushkin HP-580AP PSU.

+5V Line

This power line supplies the peripheral components and cards as well as USB devices. Again, the chart was adjusted to show you the minimum and maximum limits under the ATX12V specifications. As long as the voltage lines remain within the chart, they are within specifications.

The Mushkin HP-580AP PSU produced a very steady but high +5V voltage, which at 5.2V was just under the absolute limit of 5.25V. The COUGAR PowerX 550W PSU, on the other hand, was closer to the mark, varying between 5.0V and 5.1V.

+3.3V Line

This is the least important power line, which supplies certain peripheral components and cards. Again, the chart was adjusted to show you the minimum and maximum limits under the ATX12V specifications. As long as the voltage lines remain within the chart, they are within specifications.

Both power supply units produced a steady +3.3V voltage, but again, the Mushkin HP-580AP was on a high side with a voltage of 3.39V. The COUGAR PowerX 550W PSU, on the other hand, was right on the mark - producing exactly 3.3V.

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