Corsair has again proven that they have the power to rock the competition's boat if and when they want. Many other brands have lately focused on silent operation, and Corsair decided to react by releasing the RM series. It addresses users that want good performance, a fully modular design, and, above all, an ultra-quiet operation. The RM850 is the quietest PSU I have tested so far, fanless units not included. It owns this victory to its semi-passive operation and the specially designed fan with incredibly low noise output at even full speed. Its performance may not be ground breaking, though it is close enough to top-performing Gold units, but its top noise output easily made me give it our Highly Recommended award.

Skipping to the negatives I managed to spot: Its fan may offer an incredibly quiet operation by engaging late, but I was taken aback by the dangerously high temperatures inside the hot box, which were due to the fan's refusal to engage sooner. Such temperatures stress highly sensitive components, like capacitors, which may affect reliability down the road, yet Corsair seems to believe in this platform/design since they provide it with a five-year warranty to cover you fully should anything bad happen. The large heatsinks, and the large metal plate attached to the solder side of the main PCB, apparently absorb heat rather effectively until the fan spins up. Another downside I found was the limited functionality of the Corsair Link software, which is to be expected, though, since this unit isn't digitally controlled like those of the AXi series. The lack of digital control may be the main reason behind Corsair's decision not to include the Corsair Link cable needed for connectivity to your mainboard. It would also increase cost, and most users wouldn't pay for this feature happily since the software can in this case only monitor fan speed and +12V amperage. I also don't agree with Corsair's choice of Ltec caps in the secondary side because the unit uses a semi-passive cooling solution. Corsair surely meant to keep production cost as low as possible to price these RM units competitively, but should have at least picked Teapo caps instead since they are generally considered of higher, more acceptable quality.

To wrap up: The RM850 is right for you if noise output is your main concern and you want a well-performing PSU with great support, nice looks, and an interesting set of features. Its cost is kept at reasonable levels, and it will, in a case with good airflow, operate passively most of the time, providing you with the lowest possible noise output available outside of installing a fanless PSU.