The RM650 is dead silent and offers high overall performance, which still is 2% away from the slightly more expensive RM650x. The major differences with the latter are the less expensive bulk and filtering capacitors and the Hong Hua fan, instead of the proven NR135L which is used in all RMx units. I don't mind so much the Chinese-made caps since nowadays most caps are made in China, even some models from Japanese brands. Moreover, Corsair provides the same long warranty in both the RM and RMx units, showing its faith in the parts that CWT used. When it comes to the cooling fan, I am a huge fan of the NR135L because it has proven its worth so far, while there are several complaints about Hong Hua fans, mostly about ticking noises under low speeds.
It might lack the Japanese branded caps, the NR135L fan and it also doesn't use any extra caps on its modular cables, which is a blessing for most users though, but there are some areas where it is better than the RM650x which belongs to a higher line. For starters its efficiency is higher, especially under light loads, and it supports the new Modern Standby mode that Windows 10 introduced. This means that with the proper mainboard installed, the RM650 can wake up the system within a five second period. This new standby mode support is listed in the upcoming Intel ATX spec and most likely the RMx models will also get an update to support it. The same update should also provide higher efficiency under super light loads, in the RMx units.
The major problem of the RM650 is the small price difference with the RM650x, which offers higher overall performance and it also manages to achieve an even lower overall noise output. Currently there is only a ten-dollar (around £8) gap between those two products and it will probably affect the sales of the RM650.
With a higher price difference, the RM650 would look much more appealing, For those of you that would like to check on a different brand, there is also the similar capacity Seasonic Focus Plus Gold which offers good performance and compact dimensions. Nonetheless, Seasonic's offering is not as quiet as the RM650, but you cannot call it noisy either with an overall noise output close to 25 dB(A).
Image Credits: Tom's Hardware
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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.