Corsair RM850x White PSU Review

For anyone counting, Corsair's RM750x and RM850x are the only two RMx models available in white, and the company says it has no plans to offer the other three capacities in this distinctive color. Today's review zeros in on the RM850x White, which is architecturally identical to the black RM850x.

In order to deliver optimal ripple performance, Corsair equips its white RMx units with individually sleeved cables that have in-line capacitors. The aesthetic result of those caps might not be pleasing to perfectionists, but because of them, the RM850x's ripple suppression reaches jaw-dropping levels.

Besides its white paint job, this version of the RM850x also features a semi-passive fan mode that facilitates silent operation under light and moderate loads. Additionally, a relaxed fan profile helps minimize noise output under more taxing scenarios. Corsair paid a lot of attention to acoustics in its RMx and RMi families, and the result is impressive indeed: they're both some of the quietest PSUs in their respective classes.

With all of that said, we're not necessarily proponents of semi-passive operation, since it allows heat to build up, potentially affecting the useful life of sensitive components like electrolytic caps. We prefer the PSU's fan to at least spin slowly under light loads, continually exhausting warm air. Moreover, you cannot install semi-passive PSUs with their fan facing down, as hot air gets trapped inside. This isn't an issue for power supplies with fans that spin all of the time. But in order to enable slow rotational speeds, you need the right fan or a PWM circuit, which adds production costs.


The white RM850x is 80 PLUS Gold-certified. It is also certified by Cybenetics, carrying the ETA-A (88-91% overall efficiency) and LAMBDA-A+ (15-20 dB[A] overall noise output) badges. Corsair's protection features are comprehensive, including over-temperature protection, and the maximum operating temperature for continuous full-power delivery is 50°C.

The cooling fan uses a rifle bearing, which is something between a sleeve bearing and a fluid dynamic one. This unit's physical dimensions are on the large side, given that you'll find 1.5kW PSUs with a similar depth.

A 10-year warranty is more than ample. Clearly, Corsair is highly confident in this platform.

Power Specifications

Max. PowerAmps252570.830.8
Total Max. Power (W)850

The minor rails are very strong, delivering up to 150W maximum combined power. Contemporary PCs rely heavily on the +12V rail, though; they don't put much load on the minor rails (that's why we call them minor). Finally, the RM850x's 5VSB rail has enough capacity to meet most usage scenarios.

Cables & Connectors

Modular Cables
DescriptionCable CountConnector Count (Total)GaugeIn Cable Capacitors
ATX connector 20+4 pin (600mm)1116-20AWGYes
4+4 pin EPS12V (750mm)2218AWGYes
6+2 pin PCIe (2x650mm) 3618AWGYes
SATA (400mm+110mm+110mm+110mm)31218AWGNo
Four-pin Molex (450mm+100mm+100mm+100mm)2818AWGNo

There are enough cables and connectors to cover a PC equipped with lots of components, including three high-end graphics cards and a motherboard with two EPS sockets. Cable length is satisfactory. However, the distance between peripheral connectors is too small, at only 10cm. This should be 15cm at least.

Power Distribution

Since this PSU features a single +12V rail, we do not have anything to say about its power distribution.

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