Riotoro Enigma 850W 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 Enigma 850's efficiency at low loads, and loads from 10 to 110 percent of its maximum-rated capacity.

The PSU's efficiency is normal for an 850W Gold-rated model. As you can see, the efficiency differences between Riotoro's offering and Corsair's CS850M, based on the same platform, are minimal.

Efficiency At Low Loads

In the following tests, we measure the efficiency of the Enigma 850W 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
11.206A0.491A0.476A0.194A19.6768.321%765 RPM
23.4 dB(A)
22.439A0.980A0.984A0.396A39.7878.535%765 RPM23.4 dB(A)0.921
33.672A1.466A1.495A5.028A59.8683.674%765 RPM23.4 dB(A)0.964
44.889A1.964A1.973A0.796A79.7385.933%800 RPM25.0 dB(A)0.956

We would like to see greater than 70% efficiency with 20W load. Results in the other three tests are satisfactory, given the PSU's high capacity.

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: 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 much more efficient than the one in Corsair's CS850M.

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

Vampire power is very low. Surely this helps improve the 5VSB rail's efficiency, especially under light loads.

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 36°C (96.8°F) to 46°C (114.8°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 36°C (96.8°F) to 46°C (114.8°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 30°C (86°F) to 32°C (89.6°F).  

With up to around 330W load at +12V, noise output is low. You need to pull more than 600W in order for the fan to start spinning faster, at which point it generates more than 37 dB(A) of noise. Up above 800W, the noise level exceeds 40 dB(A).

At normal ambient temperatures, the PSU runs silently up to typical load levels. It's only when you push the Enigma that it gets louder. And even then, you probably won't find it annoying.

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  • WhyAreYou
    Great review!