Performance

We’d like to thank Drew Beckett — aka Drasnor — for putting the Potency 550W through its paces with his suite of test equipment. Without further ado, let’s see how it fared!

Testing methodology

We don’t mess around with BIOS readings at Icrontic. We came to the table armed with a DMM, digital oscilloscope and a hand-built load tester, all of which you can read about below:

Digital oscilloscope: We used a Velleman HPS40 digital oscilloscope to check the quality of the output from the Potency. This particular unit has a sample rate of 40 megasamples per second. This means that our equipment is capable of analyzing variations in the quality of the Potency’s output at up to 40 million times per second. Compare this accuracy to the typical fluctuations in quality that occur at a tiny fraction of that potential.

We’ve also configured the oscilloscope to measure the root mean square (RMS) voltage of the Potency’s output. This means that the DC components of the signal are filtered by the Velleman, allowing us to analyze the quality of the remaining fluctuations at an accuracy of 5 millivolts per division of the oscilloscope’s output.

Digital multimeter: While the oscilloscope busies itself with the fluctuations in our output, we recruited a Fluke 73 III DMM to test our DC voltage. This device will ensure that our voltage readings are accurate where the BIOS may not be.

Load testing: Our load tester is built using a 16 gauge nickel-chromium resistance wire. This nichrome wire is connected to two load generators:

• 1kW load with 12V applied to a 0.5 ohm resistor for 18A.
• 1kW load with 5V applied to a 0.25 ohm resistor for 20A.

In this case, both load sources are connected directly to the power supply with a standard molex connector.

Lastly, we triggered the power supply to run using a CoolMax PC/SPS tester. This unit will allow us to turn the power supply on and off without being connected to a motherboard, and it’s way more glamorous than a paperclip.

Results

Power supplies are designed to output steady DC current, which should be pegged at a constant voltage at all times. Sensitive electronics require the current to be steady else they may be damaged if the power is too erratic. Any voltage that deviates from a perfectly steady output is known as ripple.

We can calculate the ripple with a value called mVDC_RMS, or the average amount the line’s quality wanders away from our perfect world as measured in millivolts. Higher values for mVDC_RMS indicate a more inconsistent output from our power supply.

+5V Rail Quality

As testing began, the +5V rail started almost exactly at the desired 5V at 5.04V idle. With a heavy load applied to the +5V rail, a drop to only 4.8V was observed. While the voltage did dip slightly, it was very minor. The ripple was just plain outstanding at both idle and load.

Ripple was fairly low but had odd waveform characteristics. The waveform had nominal peak-to-peak ripple of 10 mV and a few spikes up to 30 mV. This was very good and well within the ATX specification.

At load, ripple was pretty good. Nominal peak-to-peak ripple is 15 mV, with peaks to 100 mV.

+12V Rail Quality

The +12V rail started out strong, if a touch high, at 12.37V. At full load, it dipped slightly to 12.23V. Put simply, the Potency 550 12V rail had outstanding output and ripple characteristics.

At 12V idle, peak-to-peak ripple was about 20 mV with a few small transients. This waveform would likely appear constant in motherboard monitoring software. A bit of the AC waveform from the input was visible but, overall, this was very good.

Peak-to-peak voltage was around 20 mV at load with some 100 mV peaks. Motherboard monitoring software would likely report this as constant with the occasional dip or spike.