Corsair RM Series 850 W Review 0

Corsair RM Series 850 W Review


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We would like to thank Corsair for supplying the review sample.

Corsair has hammered the PSU market with new products these last couple months. In a sudden move a few days ago, they released the RM series sitting right between the HX and TX line. All units of this series are, according to Corsair, optimized for silence, and their fully modular, low-profile, and all-black cabling solution also allows for fast and clean builds. The latter admittedly sounds a little strange since the higher HX series doesn't utilize a fully modular cabling design, but the "lesser" RM units do, and they are even Gold certified, sporting the same efficiency as the HX units. This particular setup will probably cause some internal competition, but such competition always benefits the end consumer. The series consists of six members with capacities ranging from 450 W to 1000 W, covering all market segments from mainstream to high-end. All units are Gold certified and feature a fully modular cabling design, which boosts their usability drastically.

The main subject of today's review will be the RM850, which, as its model number implies, has a capacity of 850 W, making it the second-strongest RM unit. Corsair says to have equipped this and all other RM units with low-noise capacitors and transformers, and a semi-passive operation, a nowadays often sought-after feature to drastically reduce noise output. Its fan is also custom-designed to operate quietly—Corsair states it to be whisper quiet, even at high load. Our dB meter will clearly show whether this holds true.

Another interesting characteristic of all RM units is their compatibility with the Corsair Link system, though you have to buy it separately. Corsair Link, coupled with its appropriate software suite, allows you to monitor both fan speed and +12V current directly on your desktop. However, there is a catch: You can only monitor the fan speed and not control the fan’s operation, which would definitely be useful. But the need for special circuits would also increase production cost.


Corsair RM850 Features & Specs
Max. DC Output850W
Efficiency80 PLUS Gold
Intel Haswell ReadyYes
Operating temperature0°C - 40°C
ProtectionsOver Voltage Protection
Under Voltage Protection
Over Power Protection
Over Temperature Protection
Over Current Protection
Short Circuit Protection
Cooling135 mm Fan (NR135L)
Semi-passive operationYes
Dimensions150 mm (W) x 86 mm (H) x 180 mm (D)
Weight2.2 kg
ComplianceATX12V v2.4, EPS 2.92
Warranty5 years
Price at time of review (exc. VAT)$149.99

Efficiency is 80 Plus Gold, and the unit is compatible with the newest ATX 2.4 spec (or 1.31 revision), which brings several updates over the previous version. All ATX 2.4 PSU are normally also Haswell ready, supporting the new sleep states Intel introduced with Haswell.

The RM850 has all protection features, including OTP (Over Temperature Protection), which is essential in semi-passive units, especially if their maximum operating temperature is only 40°C. We find it pretty strange that Corsair rated their new RM units at only 40°C since all RM units feature a semi-passive operation, which will inevitably lead to increased operational temperatures.

At 18 cm long, the RM850's dimensions are quite large. However, most chassis will accommodate it without a problem. Its warranty is long enough at five years, and the price Corsair asks for the unit looks pretty nice if we take its specifications and features into account.

Corsair RM850Power Specs
Max. Power25A25A70.8A3A0.8A
Total Max. Power850W

There is only one +12V rail. It can deliver the unit's full power if needed. The minor rails are very strong with 150 W maximum combined power, and the 5VSB rail has the typical current output for a unit of this capacity.

Cables & Connectors, Power Distribution

Modular Cables
ATX connector (610mm)20+4 pin
4+4 pin EPS12V (650mm)2
6+2 pin PCIe (600mm+150mm) 6
SATA (540mm+90mm+90mm+90mm)4
SATA (500mm+90mm+90mm)6
4 pin Molex (450mm+100mm+100mm+100mm)8
FDD adapter (+100mm)2
Corsair Link (800mm)1

This unit is equipped with an adequate number of cables. You have two EPS and six PCIe connectors at your disposal, and you can connect numerous drives and peripheral devices to its SATA and peripheral connectors. Cable length is also good; however, we would like the 4-pin Molex connectors to be spaced apart further, at least 13-15 cm. The Corsair Link cable has two headers that connect to the Corsair Link system sold separately; and it allows the PSU to connect with a USB header on the mainboard. All cables are 18AWG, which is the size the ATX spec recommends.

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


The PSU comes in a large box featuring a silver and grey background. At the front are a close-up of the unit's nicely designed fan grill and the series name in the top-right corner, inside a yellow frame. Right below it are a series of badges for the five-year warranty, semi-passive operation, Gold efficiency, and low-noise fan. The model number located under the aforementioned badges is given in large fonts.

This side has nothing worth commenting on.

Corsair provides a useful description of all connectors and their numbers on this side, and the description even includes cable lengths, since Corsair is familiar with the queries of users and reviewers. We wish more companies were as thoughtful as they are!

The rear has two graphs displaying the unit's efficiency curves with 230 VAC and 115 VAC power input, and the fan's noise output. According to the second graph, the fan starts to spin up after the load reaches 40% of the unit's maximum-rated capacity. We also found the power specifications table on the same side.


The PSU is surrounded by packing foam to ensure it reaches its user in pristine condition, regardless of shipping conditions. Corsair is generally very careful with their packages, which is to their own benefit since it reduces DOA (Dead On Arrival) products that would have to be RMAed—many DOA products are due to harsh shipping conditions and improper packages that provide insufficient protection.

The bundle includes the modular cables, a user's manual, a warranty leaflet, an AC power cord, enough zip ties, and a Corsair case badge. You will also get a product catalog, but our sample didn't include any fixing bolts for PSU mounting. Corsair apparently forgot to include a set since this is a review sample, but we, contrary to normal consumers, don't actually need them.

This is the optional Corsair Link cable you must purchase separately if you want to monitor the PSU's fan speed and +12V current output. Corsair chose not to include it in the bundle since it would increase the final price. Given the limited features Corsair Link provides to analog-controlled PSUs, we think they made the right choice. The Corsair Link cable attaches to a USB header on your mainboard, and you have to download the Corsair Link software to monitor fan speed and +12V current output. We wish they would also provide a USB adapter for connection to a normal USB port, which would spare us a bunch of trouble since we don't mount PSUs into a chassis, but use Chroma load stations instead.

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