To test the power supply unit, we will not connect it to an everyday system as we would be unable to know the exact load that we would provide and wouldn’t be able to vary the load. Instead we will use power resistors which are nothing more than normal resistors but capable of consuming a good amount of power. How much power depends on the resistance and capability of the resistor, and can be easily calculated by Ohm’s law ( Amperes = Voltage / Resistance, Power = Voltage * Amperage ).

Hence for example a 1Ohm resistor attached to the 3.3V line will allow 3.3A through it and consume about 10W of power. When adding two of these resistors in parallel, you double the power consumption and allow 20W to be consumed as you halve the resistance this way. Adding more will increase the power consumption. Of course that is not entirely accurate on paper as the fault tolerance of these resistors is high and almost none are exact to their resistance specifications, but after using them we could calculate how much power each bunch of them would consume accurately. This way we can add fake load to any power supply unit, and on any power line we wish with good accuracy.

For testing the DarkPower P6-470 taking into account its design and power specifications, we took the following steps:

Total Load	3.3V Load	5V Load	12V-1 Load	12V-2 Load
30% (~135W)	7A (23W)	6A (30W)	5A (60W)	2A (24W)
50% (~225W)	12A (40W)	10A (50W)	6A (72W)	5A (60W)
75% (~340W)	18A (60W)	15A (75W)	9A (108W)	8A (96W)
100% (~470W)	20A (66W)	20A (100W)	13A (156W)	12A (144W)

The room temperature when the test took place was 22 Celsius degrees. The DarkPower P6-470W worked flawlessly and met its maximum power output, although it did not surpass it. The unit would shut down in seconds if loaded any further. This seems logical as I suspect it should have an overload safety switch, plus it is already overloaded at 470W as the true maximum output through the 3.3V/5V/12V lines of the unit is 450W and the remaining 20W are reserved for the -5V/-12V/5VSB lines only.

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The voltage regulation of the unit was very good throughout the load testing, never nearly violating the ±5% rating. The 3.3V line was very strong across the load tests, while the 5V line weakened a little at full load but not to a point that can cause any concern. Both of the two 12V lines remained very strong and very close to the specifications. The unit remained completely silent even at 75% load. At 100% load the unit became audible, but never became annoying.