Home / Tech News / Featured Tech News / Corsair RM850x (2018) PSU Review

Corsair RM850x (2018) PSU Review

Rating: 8.5.

The major difference between the older RM850x and its successor is the shorter, by 20mm, depth of the new model. With the new model Corsair claim to offer excellent performance at a competitive price point, and all with no cost cutting. Our analysis will give you the answers you need to know before spending the money yourself.

Corsair decided to revamp some models of the highly popular RMx line, so they released the new RM550x, RM650x, RM750x and RM850x this year (2018) which feature smaller dimensions, thanks to the 20mm less depth.

On top of that, another major difference is that the fresh RM750x is equipped now with two EPS connectors instead of the single one that the previous model had. It would be nice if the new RM650x also had two EPS connectors, but obviously Corsair didn't want to create internal competition with the RM650i (which also has a single EPS connector).

The RM850x has to fight some formidable opponents including the EVGA SuperNOVA 850 G3 and of course the similar capacity Seasonic Focus Plus Gold. The G3 model is usually more expensive while the SSR-850FX is about the same price as the Corsair model.

Read our How We Test Power Supplies HERE


Manufacturer (OEM) CWT
Max. DC Output 850W
Efficiency 80 PLUS Gold, ETA-A (88-91%)
Noise LAMBDA-A+ (15-20 dB[A])
Modular (Fully)
Intel C6/C7 Power State Support
Operating Temperature (Continuous Full Load) 0 – 50°C
Over Voltage Protection
Under Voltage Protection
Over Power Protection
Over Current (+12V) Protection
Over Temperature Protection
Short Circuit Protection
Surge Protection
Inrush Current Protection
Fan Failure Protection
No Load Operation
Cooling 135mm Rifle Bearing Fan (NR135L)
Semi-Passive Operation ✓ (non-selectable)
Dimensions (W x H x D) 152 x 87 x 162mm
Weight 1.66 kg (3.66 lb)
Form Factor ATX12V v2.4, EPS 2.92
Warranty 10 Years

The unit is 80 PLUS Gold certified while in the Cybenetics scale it scores ETA-A and LAMBDA-A+, for efficiency and noise respectively. While a ETA-A rating is common for a high-end power supply, this is not the case with the LAMBDA-A+ rating which is very rare for a 850W unit.

The maximum operating temperature for continuous full load delivery is 50°C, as the ATX spec recommends, while all necessary protection features are present including over temperature protection, which is crucial for any PSU. The cooling duties are handled by a 135mm rifle bearing fan, which is utilized by all RMx models, both the previous and the current ones. The fan is supported by a semi-passive mode which cannot be deactivated, unfortunately.

The previous RM850x was quite large since it measured 182mm in length while the new one is 20mm shorter. This means less hassle during the installation process, especially if the PSU compartment of the chassis is small. Finally, the provided warranty is extra long at ten years, showing Corsair's and CWT's faith in this platform.

Power Specifications

Rail 3.3V 5V 12V 5VSB -12V
Max. Power Amps 25 25 70.8 3 0.8
Watts 150 850 15 9.6
Total Max. Power (W) 850

This is a single +12V rail PSU, able to deliver its full power on this rail. The minor rails are too strong for any modern system, at 150W max power combined, while the 5VSB can deliver up to three Amps, on papers at least since in reality it is much stronger.

Cables & Connectors

Modular Cables
Description Cable Count Connector Count (Total) Gauge In Cable Capacitors
ATX connector 20+4 pin (600mm) 1 1 18-20AWG Yes
4+4 pin EPS12V (650mm) 2 2 18AWG Yes
6+2 pin PCIe (600mm+150mm) 3 6 18AWG Yes
SATA (500mm+110mm+110mm+110mm) 1 4 18AWG No
SATA (520mm+110mm+110mm) 2 6 18AWG No
4-pin Molex (450mm+100mm+100mm+100mm) 2 8 18AWG No
FDD Adapter (+100mm) 1 1 20AWG No
AC Power Cord (1430mm) – C13 coupler 1 1 16AWG

There are two EPS connectors, something that we find essential in a 850W power supply. The number of PCIe connectors is satisfactory as well and the same goes for the SATA and 4-pin Molex. Corsair also provides a Berg (FDD) adapter for the users that still need it.

All cables are long enough, but the distance between the peripheral connectors is small at only 10cm. Finally, the ATX, EPS and PCIe cables feature inline caps for even better ripple suppression.

Become a Patron!

Be sure to check out our sponsors store EKWB here

Check Also

KitGuru Games: Modern Warfare II is Mechanically Perfect

Modern Warfare II (2022) represents the latest and greatest from Infinity Ward and Call of Duty, serving as a reimagining of this now 13-year-old game – offering the tried-and-true COD experience while evolving the player movement and controls in order to make it what I believe is the most mechanically perfect multiplayer FPS yet...