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Corsair RM850x White PSU Review

Load Regulation, Hold-Up Time & Inrush Current

To learn more about our PSU tests and methodology, please check out How We Test Power Supply Units. 

Primary Rails And 5VSB Load Regulation

Load Regulation testing is detailed here.

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Hold-Up Time

Our hold-up time tests are described in detail here.

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The hold-up time we measure is long at 30ms, and the delay between the power-good signal and hold-up time is pretty large, ensuring the system's safe shut-down.

Inrush Current

For details on our inrush current testing, please click here.

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With 115V input, the inrush current is quite low. It's a little higher than expected (but still fairly normal) with 230V input.

Load Regulation And Efficiency Measurements

The first set of tests reveals the stability of the voltage rails and the RM850x's efficiency. The applied load equals (approximately) 10 to 110 percent of the PSU's maximum load in increments of 10 percentage points.

We conducted two additional tests. During the first, we stressed the two minor rails (5V and 3.3V) with a high load, while the load at +12V was only 0.1A. This test reveals whether a PSU is compatible with Intel's C6/C7 sleep states or not. In the second test, we determined the maximum load the +12V rail could handle with minimal load on the minor rails.

Test #12V5V3.3V5VSBDC/AC (Watts)EfficiencyFan SpeedPSU NoiseTemps (In/Out)PF/AC Volts
15.196A1.982A1.982A0.996A84.56186.551%0 RPM<6.0 dB(A)46.18°C0.968
211.404A2.975A2.977A1.196A169.03590.208%0 RPM<6.0 dB(A)46.81°C0.988
318.022A3.473A3.460A1.397A254.17291.172%0 RPM<6.0 dB(A)47.26°C0.993
424.648A3.971A3.975A1.599A339.40491.300%0 RPM<6.0 dB(A)48.35°C0.995
530.951A4.966A4.971A1.800A424.71091.024%0 RPM<6.0 dB(A)49.07°C0.995
637.202A5.961A5.970A2.002A509.25690.493%610 RPM10.2 dB(A)41.99°C0.996
743.522A6.957A6.970A2.204A594.56489.918%655 RPM11.2 dB(A)42.50°C0.997
849.858A7.953A7.973A2.407A679.92689.206%785 RPM18.1 dB(A)43.01°C0.997
956.596A8.457A8.462A2.407A764.88588.453%943 RPM24.5 dB(A)44.22°C0.997
1063.080A8.955A8.984A3.019A849.69387.554%1154 RPM31.0 dB(A)45.81°C0.997
1170.165A8.957A8.989A3.020A934.49086.591%1415 RPM36.7 dB(A)47.43°C0.997
CL10.729A18.002A17.999A0.000A159.01683.428%785 RPM18.1 dB(A)44.25°C0.989
CL270.830A1.000A0.997A1.000A867.18587.882%1119 RPM30.0 dB(A)45.60°C0.997

Load regulation is pretty tight on all rails; everything except the 5VSB rail stays within 1% (and even then, 5VSB achieves 1.31% deviation, a new load regulation record for the 850W PSU category).

Efficiency-wise, the RM850x easily meets 80 PLUS' requirements for Gold certification, even under our hot box's very high ambient test conditions. Fan noise stays low not only because of its limited maximum speed, but also thanks to a relaxed profile. We have to push the PSU beyond its limits to make the fan spin at full speed, where it barely hits 37 dB(A).

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Aris Mpitziopoulos
Aris Mpitziopoulos is a Contributing Editor at Tom's Hardware US, covering PSUs.