Corsair RMx Series 850W Power Supply Review

A Detailed Look

The PSU ships with a label over the back panel to make sure you understand that the fan will not start spinning until the PSU is under moderate load.

The Corsair RM850x power supply enclosure is painted matte black with light gray lettering and measures 180mm (7.1”) long.  Note the beveled edges for a distinctive look. The back panel includes an On-Off switch and AC receptacle.

The power supply uses a Corsair NR135L fan that operates in silent Zero RPM mode up to ~40% load (25°C room temperature).   The NR135L intake fan was designed by Corsair to move more air through the power supply components with less noise. Fan blades are properly balanced to prevent resonance at higher RPMs and the fan features rifled bearings for quiet operation and long life. The fan is rated for 0.22A at 12 VDC.

The front panel incorporates twelve modular connectors for the power cables, all nicely keyed and labeled.

Fully Modular Cables

RM850x: (2) 4+4 pin EPS/ATX12V, (1) 24-pin ATX, and (3) PCI-E,

RM850x: (3) SATA, (2) 4-pin Peripheral, (1) FDD Adapter

The RM850x comes with a good assortment of fully modular cables and connectors. All of the cables are black, sleeved or the flat ribbon-style, which makes for easy installation with a clean look and helps optimize case airflow.

Under the Hood

Here are a few pictures showing the layout and components inside the RM850x power supply.  The RMx Series was custom designed by Corsair and manufactured by Channel Well Technologies (CWT), one of Corsair’s long standing OEM partners.

The Corsair RMx Series PSUs utilizes a modern full-bridge design with LLC resonant converter topology to minimize switching losses and help increase efficiency. Two DC-to-DC converters are used on the secondary to produce the +3.3V and +5V minor rails from the +12V main section.

All of the electrolytic capacitors used in the RMx power supply are high-quality Japanese made caps rated for 105°C operation. For example, the two bulk capacitors are made by Nichicon and rated for 470uF, 400V and 105°C. The overall component layout is clean, leaves room for good airflow and the soldering appears very good.