Corsair RM650x PSU Review

Efficiency, Temperature And Noise


Our efficiency testing procedure is detailed here.

Using the results from the previous page, we plotted a chart showing the RM650x efficiency at low loads, and loads from 10 to 110 percent of the PSU's maximum-rated capacity.

Efficiency is quite high under normal loads, and fairly good with light loads. Given the 80 PLUS Gold certification, our results fall within the expected levels.

Efficiency At Low Loads

In the following tests, we measure the RM650x's efficiency at loads significantly lower than 10 percent of its maximum capacity (the lowest load the 80 PLUS standard measures). The loads we dialed were 20, 40, 60 and 80W. This is important for representing when a PC is idle, with power-saving features turned on.

Test #12V5V3.3V5VSBDC/AC (Watts)EfficiencyFan Speed
Fan Noise
PF/AC Volts
11.206A0.491A0.481A0.195A19.6169.42%0 RPM0 dB(A)
22.444A0.990A0.995A0.395A39.7780.21%0 RPM0 dB(A)0.933
33.680A1.477A1.509A5.028A59.8384.61%0 RPM0 dB(A)0.959
44.907A1.985A1.990A0.795A79.7686.90%0 RPM0 dB(A)0.976

We would like to see higher than 70% efficiency with 20W load, though the PSU performs well in the other three tests. It's also worth mentioning that the RM650X's fan didn't spin during our low-load benchmarks.

5VSB Efficiency

The ATX specification states that 5VSB standby supply efficiency should be as high as possible, recommending 50 percent or higher with 100mA of load, 60 percent or higher with 250mA of load, and 70 percent or higher with 1A or more of load.

We take four measurements here: one each at 100, 250 and 1000mA, and one with the full load the 5VSB rail can handle. 

Test #5VSBDC/AC (Watts)EfficiencyPF/AC Volts

The 5VSB rail is highly efficient, losing only to FSP's HG650 and its advanced 5VSB circuit.

Power Consumption In Idle And Standby

In the table below, you'll find the power consumption and voltage values of all rails (except -12V) when the PSU is idle (powered on, but without any load on its rails), and the power consumption when the PSU is in standby mode (without any load, at 5VSB).

Mode12V5V3.3V5VSBWattsPF/AC Volts

The RM650x easily meets the ErP Lot 6 2013 directive's requirements.

Fan RPM, Delta Temperature And Output Noise

Our mixed noise testing is described in detail here.

The first chart below illustrates the cooling fan's speed (in RPM), and the delta between input and output temperature. The results were obtained at 37 °C (98.6 °F) to 49 °C (120.2 °F) ambient temperature.   

The next chart shows the cooling fan's speed (again, in RPM) and output noise. We measured acoustics from one meter away, inside a small, custom-made anechoic chamber with internals completely covered in sound-proofing material (be quiet! Noise Absorber kit). Background noise inside the chamber was below 18 dB(A) during testing, and the results were obtained with the PSU operating at 37 °C (98.6 °F) to 49 °C (120.2 °F) ambient temperature. 

The following graph illustrates the fan's output noise over the PSU's operating range. The same conditions of the above graph apply to our measurements, though the ambient temperature was between at 28 °C (82.4 °F) to 30 °C (86 °F).  

This is one of the quietest 650W PSUs we've tested. If you need a high-performance power supply that's almost always silent, the RM650X is a worthy candidate.