Corsair RM850x ATX 3.1 Power Supply: features, specs and who it suits

The Corsair RM850x is a fully modular ATX power supply built for desktop PCs. It is part of Corsair's RMx series and meets the newer ATX 3.1 standard, with a native 12V-2x6 connector for current graphics cards. This page explains what those terms mean and what to confirm before choosing a power supply.

Fully modular cabling

With a fully modular unit, every cable plugs into the power supply rather than being fixed to it. You connect only what your system needs, which reduces clutter and helps airflow. Corsair describes the cables as embossed, flexible and fitted with low-profile combs, which hold the wires in neat rows and make routing easier in tight cases.

Cybenetics Gold efficiency

Corsair says the RM850x is Cybenetics Gold certified, with efficiency of up to 91%. Efficiency is the share of the power taken from the wall that actually reaches your components. The rest becomes heat. A more efficient unit typically wastes less energy and needs its fan less often. Cybenetics is an independent testing body that grades power supplies, and its Gold level is broadly comparable to the 80 PLUS Gold tier, though the test methods differ.

ATX 3.1, PCIe 5.1 and the 12V-2x6 connector

ATX 3.1 is Intel's current power supply standard. Corsair says the RM850x supports PCIe 5.1 and is designed to resist the brief power spikes that modern graphics cards can create. The native 12V-2x6 connector means a compatible graphics card can plug straight into the supply, without an adapter. Cards that still use older 8-pin connectors need the usual PCIe cables instead, so check which kind yours uses.

Components and cooling

The listing says the unit uses 100% Japanese 105°C-rated electrolytic capacitors. Capacitors smooth the power that reaches your components, and a higher temperature limit generally gives more margin inside a warm case. Cooling comes from a 140 mm fan with a fluid dynamic bearing (FDB), a design that is typically quiet and long-lived compared with simpler sleeve bearings. Corsair markets the unit as low-noise.

Warranty

Corsair backs the RMx series with a ten-year warranty. Read the terms before you rely on it, as conditions vary by region.

Who it suits

An 850W unit leaves room for a mid-range or high-end gaming PC, or a workstation with a powerful graphics card and several drives. It is a full-size ATX unit, so it fits standard ATX cases.

What to check before you buy

• Power needs: add up the rated power of your processor and graphics card, and leave some headroom.
• Connectors: confirm what your graphics card needs, whether 12V-2x6 or 8-pin cables.
• Case fit: check that your case takes a standard ATX power supply and has room for the cables.
• Cable length: large cases may need longer leads, so compare against the cable lengths in the manual.
• Compatibility: check the motherboard's power connectors against the cables included.
• Installation: switch off and unplug the system, and follow the manual.

The short version

• A fully modular 850W ATX power supply from Corsair (model CP-9020270-NA).
• Cybenetics Gold certified, with efficiency of up to 91%.
• ATX 3.1 compliant, with PCIe 5.1 support and a native 12V-2x6 connector.
• 140 mm FDB fan and 105°C-rated Japanese capacitors, plus a ten-year warranty.
• Weighs about 3.9 lb (1.8 kg).

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