Corsair RM850 Power Supply Review: A Solid Value

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Protection Features, DC Power Sequencing, Cross-Load Tests and Infrared Images

Protection Features

Check out our PSUs 101 article to learn more about PSU protection features.

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Protection Features
OCP12V: 88.4A (124.86%), 11.973V 5V: 29A (145%), 5V 3.3V: 30A (150%), 3.301V 5VSB: 5.4A (180%), 4.898V
OPP1076.5W (126.65%)
OTP✓ (140°C @ 12V heat sink)
SCP12V: ✓ 5V: ✓ 3.3V: ✓ 5VSB: ✓ -12V: ✓
PWR_OKProper Operation
SIPSurge: MOV Inrush: NTC Thermistor & Bypass Relay

The triggering points of the Over Current Protection (OCP) on the minor rails are quite high, but they don't affect the load regulation. The 5VSB rail can also deliver much more power than its nominal, which may come in handy though, because the modern standby modes will put a heavy burden on this rail.

The Over Power Protection (OPP) is properly set, and there is Over Temperature Protection, which shuts down the PSU before the secondary heat sink gets overheated.

DC Power Sequencing

According to Intel’s most recent Power Supply Design Guide (revision 1.4), the +12V and 5V outputs must be equal to or greater than the 3.3V rail at all times. Unfortunately, Intel doesn't mention why it is so important to always keep the 3.3V rail's voltage lower than the levels of the other two outputs.

No problems here, since the 3.3V rail is always lower than the other two.

Cross Load Tests

To generate the following charts, we set our loaders to auto mode through custom-made software before trying more than 25,000 possible load combinations with the +12V, 5V, and 3.3V rails. The deviations in each of the charts below are calculated by taking the nominal values of the rails (12V, 5V, and 3.3V) as point zero. The ambient temperature during testing was between 30 to 32 degrees Celsius (86 to 89.6 degrees Fahrenheit).

Load Regulation Charts

Efficiency Chart

The above graph, clearly shows the high efficiency levels under light loads. If Corsair had set the maximum combined power of the minor rails at a lower level, since 150W is too much for any modern system, the overall efficiency would be even higher since the more you stress the DC-DC converters that generate the 5V and 3.3V rails, the higher are the energy losses on them.

Ripple Charts

The lower the power supply's ripple, the more stable the system will be and less stress will be also applied to its components.

Infrared Images

We apply a half-load for 10 minutes with the PSU's top cover and cooling fan removed before taking photos with a modified FLIR E4 camera able to deliver an IR resolution of 320x240 (76,800 pixels).

Inside the power supply, the temperatures are at normal levels. As expected, the hottest part is the board hosting the +12V FETs, which is close to the DC-DC converters board.

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Contributing Editor

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