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Corsair RM850x V2 PSU Review: Smaller And Quieter!

Efficiency, Temperature & Noise

Efficiency

Our efficiency testing procedure is detailed here.

Using results from the previous page, we plotted a chart showing the RM850x’s efficiency at low loads, and loads from 10 to 110 percent of its maximum-rated capacity.

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The PSU's efficiency is high under normal loads. Meanwhile, efficiency is satisfactory under light loads, but certainly not the best we've seen.

Efficiency At Low Loads

In the following tests, we measure the RM850x'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 SpeedPSU NoisePF/AC Volts
11.201A0.491A0.481A0.195A19.68566.867%0 RPM<6.0 dB(A)0.878
12.187V5.036V3.316V5.030V29.439115.10V
22.424A0.989A0.994A0.396A39.80178.444%0 RPM<6.0 dB(A)0.941
12.185V5.035V3.315V5.028V50.738115.10V
33.650A1.476A1.504A5.023A59.88283.029%0 RPM<6.0 dB(A)0.966
12.184V5.035V3.314V5.023V72.122115.10V
44.861A1.984A1.991A0.796A79.79986.345%0 RPM<6.0 dB(A)0.975
12.182V5.035V3.314V5.019V92.419115.09V

We would like to see close to 70% or better under 20W of load, while it'd be nice to see greater than 80% efficiency with 40W.

5VSB Efficiency

The ATX specification, along with CEC, ErP Lot 3 2014 and ErP Lot 6 2010/2013, states that 5VSB standby supply efficiency should be as high as possible, recommending 75 percent or higher with 550mA, 1A, and 1.5A of load. The PSU should also achieve higher than 75% efficiency at 5VSB under full load, or with 3A if its max current output on this rail is higher than 3A.

We take six measurements: one each at 100, 250, 550, 1000, and 1500mA, and one with the full load the 5VSB rail can handle.   

Test #5VSBDC/AC (Watts)EfficiencyPF/AC Volts
10.101A0.51376.000%0.067
5.055V0.675115.11V
20.251A1.27078.882%0.126
5.051V1.610115.44V
30.542A2.73378.920%0.256
5.042V3.463115.07V
41.002A5.03777.792%0.345
5.028V6.475115.07V
51.501A7.53077.413%0.393
5.015V9.727115.08V
63.001A14.92075.998%0.454
4.971V19.632115.08V
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The previous RM850x demonstrated notably higher 5VSB efficiency.

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
Idle12.211V5.038V3.316V5.036V7.1470.434
115.1V
Standby0.0420.005
115.1V
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Vampire power is very low with both voltage inputs.

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 47°C (116.6°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 hemi-anechoic chamber. Background noise inside the chamber was below 6 dB(A) during testing (it's actually much lower, but our sound meter’s microphone hits its floor), and the results were obtained with the PSU operating at 37°C (98.6°F) to 47°C (116.6°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 30°C (86°F) to 32°C (89.6°F).  

Semi-passive operation doesn't last long in our cross-load tests because we start with a high load on the minor rails. Still, the fan spins slowly through most of the PSU's operating range. There's only a small window where noise lands within the 25-30 dB(A) range. In general, the fan profile is conservative, keeping the RM850x V2's noise levels low.

MORE: Best Power Supplies

MORE: How We Test Power Supplies

MORE: All Power Supply Content

  • parkerygc8
    Sweet, first review of this I've seen. Thanks.
    Reply
  • leclod
    I didn't go into detail, but I wonder what's the use of that Gold PSU when there's a Seasonic Focus Plus Platinum 750 for a similar price ?
    Reply
  • Aris_Mp
    Gold, Platinum, it doesn't really matter at this efficiency point. What matters the most, in my opinion at least, is noise output now besides the basic (reliability and overall performance).
    Reply
  • powernod
    At last some scoring at the review conclusion!! I always considered the lack of score as Tom's greater weakness about their reviews !!
    Reply