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Corsair RM850x (2021) Power Supply Review

The Corsair RM850x is the new leader in the 850W Gold category.

Corsair RM850x (2021)
(Image: © Tom's Hardware)

Performance Rating

(Image credit: Tom's Hardware)

The new RM850x leads the category, in overall performance. 

Noise Rating

The graph below depicts the cooling fan's average noise over the PSU's operating range, with an ambient temperature between 30 to 32 degrees Celsius (86 to 89.6 degrees Fahrenheit).

(Image credit: Tom's Hardware)

The difference in noise output compared to the previous model is notable. This has to do with the fan speed profile and the different fan. 

Efficiency Rating

The following graph shows the PSU's average efficiency throughout its operating range with an ambient temperature close to 30 degrees Celsius.

The new platform is more efficient than the older one, but still there is room for improvement. 

Power Factor Rating

The following graph shows the PSU's average power factor reading throughout its operating range with an ambient temperature close to 30 degrees Celsius.

Corsair RM850x (2021)

(Image credit: Tom's Hardware)

The APFC converter achieves top performance with both 115V and 230V input. 

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Aris Mpitziopoulos
Aris Mpitziopoulos is a Contributing Editor at Tom's Hardware US, covering PSUs.
  • Isokolon
    shame they changed the fan. the 2015 & 2018 RMx were so great for low-noise enthusiasts.
    how the review classifies an almost 30db unit as "quiet" is beyond me.
    Reply
  • Udyr
    What makes this unit better than the Toughpower GF1?

    https://www.tomshardware.com/reviews/thermaltake-toughpower-gf1-850w-power-supply
    Reply
  • g-unit1111
    I have an RM750x and it is a really great PSU. You can't go wrong with this unit.
    Reply
  • jsz031
    Hi Aris.. like your reviews..

    small question. I noticed the Bulk/hold up caps get higher with wattage. can you explain how this impacts a general PSU?

    for example/off topic, I have a 5 year old 550w G2 and it has a 400v 470uf cap. Just purchased a 550w g3 and the cap is lower capacity @ 400v 390uf.

    Does this mean anything or am I overthinking it? is the 550w g2 better than "base" spec? I understand leakage can occur over time, I'm just not sure if its a downgrade or upgrade in specific areas.

    thank you.
    Reply