Power supplies with 750 to 850 watt are very popular among enthusiasts with serious gaming rigs. We tested and compared 30 different models.
If you are configuring a gaming pc with a powerful graphics card you will most likely be choosing a power supply of 750 to 850 watts. Our test system consists of a Core i7 3960X, a X79 motherboard and a single SSD, paired with a high end graphics card it will draw around 305 to 400 watt on average. Obviously a socket 1150 based system will use less, but especially if you start over clocking you can easily use another 100 watts. Considering that power supplies are the most efficient when operating between 50 and 70 percent of their maximum wattage a 750 watt power supply is a good choice for a gaming rig. With a 850 watt model you could start looking at adding a second graphics card. Another thing to consider is that the fan inside a power supply will start to spin faster as you are drawing more watts from it, thus creating more noise.
The amount of power supplies you can choose from in this segment is massive. We asked several large brands to sent us their latest models and together with some previously tested models we have a total of 30 different models for this test.
How do we test power supplies?
For testing power supplies we utilise professional Stratron load generators, which allows us to put a load of up to 1600 watts on PSUs in our test lab. Each PSU we test in increments of 100 watts up to the maximum load. At each step we measure voltages on the different lines. The closer those measurements are to the official values of 3.3, 5 and 12V, the better. More than 5 percent deviation means not good. At each step we also measure the current from the socket with a professional Zes Zimmer ammeter. Based on this we calculate the efficiency. An oscilloscope allows us to measure the ripple, which are fluctuations in the direct current (dc) output of a power supply which has been derived from an alternating current (ac) source.
It should be noted that in all cases we draw 50 watts of current from the 3.3 and 5V lines, and the rest from the 12V lines. This is different than how the 80 Plus initiative or most manufacturers themselves test their power supplies, but is closer to real-world performance. In a PC all energy-consuming components (mainly the CPU and GPU) only utilise the 12V lines, and the 3.3 and 5V lines have a very limited role.
In addition to our usual testing starting at 200 watts we recently also started taking measurements at 22,5, 50 and 100 watt. We distributed the load across the 3,3, 5 and 12 volt rails just like an actual system would. We reproduced the use after an Intel Core I7 4770K Haswell-processor, a Gigabyte GA-Z87X-UD3H motherboard, two Corsair Vengeance Pro memory modules, a OCZ Vertex 4 SSD and a CPU cooler.
The 22,5 watt test is similar to the idle state of this system, the 50 watt test is similar to a situation in which a single CPU core is being used and the 100 watt test is a scenario in which whole CPU is at 100 per cent load.
Lastly we also measure the current drawn from the socket without any load. It is important to know how much leakage current a power supply has.
We have revised the way we measure noise levels. We test power supplies in a sound-proof box, so we can accurately register levels as low as 18 dB(A). We measure the sound level from a distance of 10 cm cm from the PSU, and we put 100W, 300W and 500W loads on it.
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