Corsair RM650 Power Supply Review Introduction

Corsair is perhaps the most active company in the PSU market this year, which may be slightly ironic, as they originally were a memory manufacturer that diversified into the PSU market just a few years ago. Apparently, the tens of products which they have been marketing via their six PSU series were not enough, leading Corsair to develop a seventh, new series. Today, the company’s new power supply series, the RM, is a fact, bringing 6 new units into their already crowded power supply ranks. The smallest power supply of the series starts at 450 W and the most powerful version reached up to 1000 W. Today we are having a close look at the RM650 which, as the name implies, is the 650 W version.

The company claims that the new RM power supplies are optimized for silent operation, yet that does not mean that being quiet is all these units are good at. A simple look at their specifications and an advanced computer user can identify many interesting features; a fully modular design, an 80Plus Gold certification, a single 12 V rail design and Corsair Link capabilities are just a few. Furthermore, the MSRP prices of the new units, as they can be seen in the table below, are very interesting to say the least.
















According to the table above, the new RM units end up retailing cheaper than not only the high-end HX series but the mainstream TX series as well, which perhaps is an indication that other series will be receiving price cuts or end to exist.

Corsair RM650

Corsair RM650 Features and Specifications


Five years


150mm x 86mm x 160mm




650 Watts

80 Plus


ATX Connector


EPS Connector


PCI-E Connector


4 Pin Peripheral Connector


SATA Connector


Floppy Connector



100,000 hours


Packaging and bundle

The box

The new RM650 power supply comes in a silvery, large cardboard box with a serious, professional theme. It is a very sturdy packaging and the PSU receives further protection by polyethylene foam slabs, ensuring its safe transportation.

The box (rear)

The rear side of the packaging essentially is a small manual. A table with the electrical specifications of the RM650 can be seen at the lower right corner, two graphs displaying the efficiency and the acoustics of the power supply have been plotted on the top left corner and a short presentation of its most vital features has been printed in several languages.

Bundled items

Corsair supplies little more than the bare essentials with the RM650. Inside the box we only found an AC power cable, a few cable ties, four black mounting screws, a case badge, a basic manual and warranty guide, as well as an advertising leaflet with Corsair’s most popular products.

The cables

As this is a fully modular power supply, a bunch of cables is supplied alongside it but without a pouch/purse to store them in. Each and every cable, including the 24-pin ATX cable, consists of all-black wires which have been bonded together, forming “flat-type” cables, without any form of extra sleeving. The 650W version offers four 8-pin PCI Express connectors, seven Molex connectors and eight SATA connectors, as well as the standard 24-pin ATX and 8-pin EPS connectors. Corsair also supplies two Molex to floppy adapters. A cable is also supplied which can be used to connect the RM650 to a Corsair Link hub (not included with the PSU), allowing the users to monitor the fan’s RPM and 12V line current from their desktops.

External design of the Corsair RM650

The Corsair RM650 PSU

Corsair certainly tried to make the RM series unique. At 160 mm, the chassis of the RM650 is slightly longer than that of a typical ATX power supply, yet it should fit in all but the most compact of cases. The chassis also has trimmed side edges and a ribbed design embossed at the bottom of the chassis, which serves as an extension of the design of the unique fan guard. The entire unit has been sprayed with the same matte black paint that Corsair is usually using.

Side stickers

Decorative stickers cover the sides of the RM650. Although the stickers take up most of the surface, they blend in with the color of the chassis, leaving only the company and model logos clearly visible.

Top side sticker

The sticker with the electrical specifications of the RM650 has been placed on the top side of the chassis, where it will be visible through a windowed side panel only if the case has the PSU mounting area towards its bottom and the unit's fan is still facing downwards.

Rear Side

As this is a fully modular power supply, the rear side of the chassis is mostly taken by the modular cable connectors. There are two connectors for the single 24-pin ATX cable, three connectors for the PCI Express and EPS cables, four connectors for the SATA/Molex device cables and a single connector for the Corsair Link interface cable.

Front Side

The front side of the RM650 is the standard perforated honeycomb mesh design, with only the standard on/off switch and power plug receptacle are to be found, as well as a small sticker with the unit's model.

Internal design of the Corsair RM650

The cooling fan

The 135mm fan of the RM650 has been rebranded with Corsair’s own logo. The part number is NR135L and little we could find about the OEM of the fan. However, we could recognize that it has a fluid dynamic bearing and a maximum speed of about 1800RPM. The design of the fan is supposed to be optimized in order to reduce noise, even if the fan will not even come on if the load will not surpass about 35% of the unit’s capacity.

Inside the Corsair RM650 unit

The OEM of the RM650 is easily recognizable, even if only by the type of the main transformer installed. Channel-Well Tech (CWT) is the company behind the RM650, an OEM sharing a long history with Corsair as they have been supplying nearly half of Corsair’s power-related products. The build quality is well above average and, although it is aesthetically displeasing, a lot of glue has been used in order to enhance the mechanical cohesion of the unit.

The filtering stage

The filtering stage of the RM650 is very good, starting with two Y capacitors at the back of the AC receptacle and continuing on the main PCB with two more Y capacitors, two X capacitors, two filtering chokes and one surge suppressing MOV.

Primary side

There is one main heatsink which holds the primary bridge rectifier, the active components of the APFC circuit and the primary inversion stage transistors of the power supply. The passive APFC components are a single Matsushita 400 V / 470 uF capacitor and a very large coil, wrapped in green tape, with the active components being two transistors and a diode. Despite the 80Plus Gold certification, CWT managed to achieve it with a half-bridge topology.

Secondary side

This power supply generates only a single 12 V line and the minor 3.3 V / 5 V lines are being derived by DC to DC converters, which have been placed on the vertical PCB near the edge of the unit. The small transformer is dedicated to the 5VSB voltage line. Most of the secondary side capacitors have been made by CapXon, with very few supplied by Nippon Chemi-Con. CapXon is a manufacturer considered to be mediocre by enthusiasts, yet Corsair apparently is placing a lot of faith on them, as the RM650 is covered by a 5 year warranty.

Test setup

The load

In order to be able to effectively and efficiently test any computer power supply unit, we developed and constructed our own proprietary testing station. Our testing station consists of a number of power resistors and small capacitors, which in turn are connected to a RS485 electronic relay array which allow our load to be controlled through computer software alone.

USB interface and connection panel

When accuracy and speed are of critical importance, a simple multimeter or voltage meter is not sufficient for the task. To ensure the quality of our testing, an USB laboratory interface is being used to continuously monitor and record the readings of all voltage lines simultaneously. For ripple measurements, an oscilloscope is necessary and we chose the USB Instruments Stingray, the most widely used oscilloscope amongst low voltage PSU engineers and testers.

Measurement instruments

For accurate testing and repeatable results, a stable power input is also required. Thus, we are providing power to our test samples through a 3kVA VARIAC which allows us to control the input voltage of our test samples and also perform efficiency tests under both 110V AC and 230V AC input. A Lutron DW-6091 is also being used, monitoring the input voltage, real and apparent power, power factor and amperage.

The software

A power supply testing procedure would not be complete without thermal and acoustics tests. For our acoustics tests we are using a SL-5868P digital sound level meter, placed 1 meter away from the unit (DIN standard). Two PT100 sensors and their respective displays are being used to monitor the ambient temperature and the exhaust temperature of the unit.

Complete test setup during trial run

Testing results (Regulation & Ripple)


The electrical performance of the RM650 is remarkably good, especially for the price of the power supply. Voltage regulation is quite tight, with the voltage lines deviating less than 1.5% across the load range. Ripple suppression is very good, especially considering the class of the power supply, with the maximum recorded ripple being 40 mV on the 12 V line and while the power supply was operating at maximum capacity.

Testing results (Efficiency, Noise and Thermal)


The RM650 comes with an 80Plus Gold efficiency certification, therefore we were not surprised by the excellent electrical efficiency results. At 50% capacity and with a 230 VAC input, the efficiency of the RM650 is at 92.1%, just a breath higher than the 92% 80Plus Gold specification limit. If the input voltage drops to 110 VAC, the efficiency takes a hit of about 1.1% across the entire load range, yet the RM650 still easily fulfills the 80Plus Gold certification requirements.


We recorded no noise level readings up to 40% load because the fan was entirely stopped up to that point. When we switched to 40% load, the fan started after a few seconds, yet it may only be heard if someone places an ear very close to it. As the load increased further, so did the speed of the fan, which however became clearly audible only when the load exceeded 80% of the unit’s capacity.


As the fan did not spin at <40% load, we did not take any temperature readings, as without any airflow any figures would be essentially incorrect. Above 40% load, after the fan starts spinning, the high efficiency of the RM650 helps it maintain low temperatures even while the fan is spinning very slowly. Under maximum load, the temperature delta reached up to 7.2 °C. 

Corsair RM650 Power Supply Review Conclusion

Corsair’s power products have a very good reputation amongst enthusiasts and the RM650 reminded us why. Although it does not set any new performance records, the power supply brings an excellent balance between quality, appearance and performance, which is difficult to compete with.

Bearing an 80Plus Gold certification and delivering excellent electrical and thermal performance figures, the overall performance of the RM650 is undeniably exceptional for a mainstream-class product. The power supply exhibits great voltage regulation and ripple suppression, while the high efficiency helps it to maintain low running temperatures. Not only that, but the ultra-quiet operation will certainly gain the RM series a lot of fans.

Inside the Corsair RM650 unit

The appearance of the RM650 is, in our opinion, a great asset as well. There are few, if any, fully modular 80Plus Gold certified power supplies within its price range. Corsair did not stop on the modular design however, as the RM650 also features a very nicely designed chassis and a full set of all-black, flat cables. The combination of the above makes the RM650 a visually enchanting product, which will easily draw the attention of modders and enthusiasts.

Quality-wise, CWT has always been an excellent OEM of mainstream and high performance power supplies. As such, the RM650 is clearly very well made and should prove to be a very reliable product. The use of CapXon capacitors might dishearten some enthusiasts; however, any concerns should be alleviated by the 5 year warranty that Corsair covers this unit with.

The Corsair RM650 PSU

Although Corsair is marketing the RM series as products optimized for silent operation, these power supplies obviously can offer much more and to a far greater variety of users. Furthermore, the very aggressive pricing suggests that Corsair is planning to make the new RM series their new best-seller. At this time, the RM650 can be pre-ordered for $119.99, a price which is hard to beat for the features and performance that this power supply offers. The expected release date from Newegg is 10/30/2013, so it looks like you'll have to wait a month to get one of these!

LR Recommended Award

Legit Bottom Line: Corsair’s new RM650 probably is the best PSU of its price range that hit the market in the past few months. If you are looking a balanced, quiet power supply with excellent overall performance and for a fair price, it should be in the first few spots of your shortlist.