Corsair RM850i Fully Modular 850W Power Supply Review

Introduction and Features

Fully modular and optimized for quiet operation and high efficiency.

Introduction

Corsair offers a large selection of PC power supplies and today we will be taking a detailed look at their new RM850i PSU. The RMi Series includes four models: the RM650i, RM750i, RM850i, and RM1000i. As you can see in the diagram below, the RMi Series is located squarely in the middle of Corsair’s power supply lineup. Corsair currently offers thirty four different models ranging from the 350 watt VS350 all the way up to the king-of-the-hill 1,500 watt AX1500i.

Corsair PSU Comparison

The new Corsair RMi Series power supplies are equipped with fully modular cables and optimized for very quiet operation and high efficiency. RMi Series power supplies incorporate Zero RPM Fan Mode, which means the fan does not spin until the power supply is under a moderate to heavy load. The cooling fan is custom-designed for use in PSUs to deliver low noise and high static pressure. All of the RMi Series power supplies are 80 Plus Gold certified for high efficiency.

The Corsair RMi Series is built with high-quality components, including all Japanese made electrolytic capacitors, and Corsair guarantees these PSUs to deliver clean, stable, continuous power, even at ambient temperatures up to 50°C. Each RMi Series power supply also supports Corsair’s Link software to monitor various power supply parameters and enable/disable OCP on the +12V outputs.

RMi vs. RM Series Advantages

Corsair has incorporated a number of enhancements, which differentiate the new RMi Series from the original RM Series. Here is an overview:

•    RMi Series comes with a 7-year warranty, instead of the RM’s 5-years
•    ALL Japanese made capacitors ensure long life and best in class performance
•    RMi Series is rated for full output at 50°C, instead of 40°C
•    Fluid Dynamic Bearing fan delivers longer life than RM’s rifle-bearing fan
•    Additional Corsair Link control capabilities and features

And for all these additional features, you only pay ~$10 USD price premium!

Corsair RM850i PSU Features summary:

•    850W continuous DC output (up to 50°C)
•    7-Year Warranty and Comprehensive Customer Support
•    80 PLUS Gold certified, at least 90% efficiency under 50% load
•    Corsair Link ready for real-time monitoring and control
•    Ability to switch between single and multiple +12V rails
•    Fully modular cables for easy installation
•    Zero RPM Fan Mode for silent operation up to 40% load
•    Quiet fluid dynamic fan bearing for long life and quiet operation
•    High quality components including all Japanese electrolytic capacitors
•    Active Power Factor correction (0.99) with Universal AC input
•    Safety Protections : OCP, OVP, UVP, SCP, OTP, and OPP
•    MSRP for the RM850i : $159.99 USD

PSU Testing Methodology

Establishing an accurate load is critical to testing and evaluating a PC power supply.  PCPerspective’s power supply test bench can place a precise DC load on the PSU under test.  Each power supply is tested under controlled, real-world conditions up to its maximum rated load (at 40ºC), using both 115 VAC and 240 VAC line voltage.  Our current suite of tests includes:

•    DC Load Regulation
•    AC Ripple and Noise
•    Efficiency
•    Differential Temperature
•    Noise

The Corsair RM850i power supply was evaluated on both features and performance.  A full range of equipment was used to test the power supply under controlled load conditions.  

•    (2) CSI3710A Programmable DC load (+3.3V and +5V outputs)
•    (4) CSI3711A Programmable DC load (+12V)
•    (3) 218W Precision resistor load bank (+12V)
•    Switchable precision resistor load bank (-12V and +5VSB)
•    Agilent 34401A digital multimeter (Accuracy ±0.0035% vDC)
•    Extech 380803 Power Analyzer (Accuracy ±0.5% of full scale)
•    DS1M12 "StingRay" digital oscilloscope (20M S/s with 12 Bit ADC)
•    Powerstat Variable Autotransformer, 1.4 KVA, 0-140 VAC
•    Extech Model 407738 digital sound level meter (Accuracy ±1.5 dB)

The following cables/connectors were used to connect the RM850i to the PCPerspective power supply test equipment.
•    (1) 20+4 pin ATX
•    (2) 8-pin EPS/ATX12V
•    (6) 6-pin PCI-E
•    (2) SATA
•    (2) Molex