It can't be easy to upgrade a platform that was already among the best in the Gold efficiency category, but Corsair managed to do it with CWT's help. The new Corsair RM850x achieves higher overall performance than its predecessor thanks to its amazing ripple suppression, tighter load regulation and higher efficiency, especially at light loads. The hold-up time is also longer, while inrush currents remain at the same low levels. The only sections where the old RM850x prevails are transient response at 3.3V, which is not of great importance, and noise output because of the more aggressive fan speed profile and the new ML fan of the new unit. Despite the increased overall noise output, we still prefer the new ML fan because it is super reliable even under high operating temperatures.
The competition in the 850W Gold efficiency category is fierce but the new Corsair RM850x achieves first place in our overall performance chart, with the Super Flower Leadex III unit following. The latter has been replaced by the Leadex V model, which we haven't received yet, for review. Other notable mentions in this category are the XPG Core Reactor 850W, the Cooler Master V850 Gold V2, and the Corsair RM850 which has a lower price tag than the RM850x.
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Disclaimer: Aris Mpitziopoulos is Tom's Hardware's PSU reviewer. He is also the Chief Testing Engineer of Cybenetics and developed the Cybenetics certification methodologies apart from his role on Tom's Hardware. Neither Tom's Hardware nor its parent company, Future PLC, are financially involved with Cybenetics. Aris does not perform the actual certifications for Cybenetics.