Cold Test Results

For the testing of PSUs, we are using high precision electronic loads with a maximum power draw of 2700 Watts, a Rigol DS5042M  40 MHz oscilloscope, an Extech 380803 power analyzer, two high precision UNI-T UT-325 digital thermometers, an Extech HD600 SPL meter, a self-designed hotbox and various other bits and parts. For a thorough explanation of our testing methodology and more details on our equipment, please refer to our How We Test PSUs - 2014 Pipeline post.

The latest version of the RM850x easily honors its 80Plus Gold certification regardless of the input voltage. We recorded an average nominal load range (20% to 100% of the unit's capacity) efficiency of 91.7% with an input AC voltage of 230V, which drops down to 89.6% if the input AC voltage is 115V. The maximum efficiency appears at 50% load and is 92.7% and 90.6% with an input voltage of 230V AC and 115V AC respectively. Even though our ambient temperature is a little higher than the 25 °C recommended by the directive, the RM850x surpasses the minimum 80Plus Gold requirements across its entire nominal load range. At sub-20% loads, the efficiency degrades significantly but the RM850x is comparatively better than most competitive products.

Corsair's engineers managed to design the RM850x so as to operate without using its fan even when the load is considerable. The fan of our test sample started when the load exceeded 220 Watts, a very significant power figure, meaning that the cooling fan will most likely never operate while the system is idling or while performing basic tasks. Regardless of the fan staying still, the operating temperatures of the RM850x remain relatively low. When the fan starts, it remains practically silent until the load is greater than 450 Watts, at which point the fan will speed up significantly. Though even then, the sound pressure levels are very low, far lower than what an average graphics card outputs under load.

The Corsair RM850x (2018) PSU Hot Test Results (~45°C Ambient Temperature)
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  • austinsguitar - Wednesday, August 22, 2018 - link

    picked this thing up for 99 dollars last week at best buy. Super quiet most of the time. Love it... capacitors in the wires are huge...
  • Cellar Door - Wednesday, August 22, 2018 - link

    It would cost Corsair less then $0.50 to include a ball bearing version o the fan.
  • philehidiot - Thursday, August 23, 2018 - link

    Do remember volume. That $0.50 might do a couple of things. Firstly when multiplied by a lot of units that becomes $0.50 x lots. Which is (($0.50)lots). Which is a lot. The other issue is if you push that onto the consumer then it may send the price over a psychological threshold which has been shown to lead to reduced overall sales. Whilst the individual is rational and when informed would rather spend $0.50 for the nice fan, the herd acts like a bunch of morons who need to be carefully led.

    This presents a problem because cows are stupid, but you want their milk.
  • Cellar Door - Thursday, August 23, 2018 - link

    Terrible analysis - higher volume means lower overall costs. As Corsair already uses higher quality fans in other units.
  • philehidiot - Wednesday, June 30, 2021 - link

    My comeback is a few years late. But you can only reduce costs with economies of scale so far. Some parts are fundamentally more expensive and the producers still need to make a profit. Last company I saw focus purely on volume, relying on economies of scale, went very bust very quickly. As I said, it might be that psychological threshold or just plain budget that they have to keep under. The other models might have had room in the budget for the ball bearing fan. Or, quite possibly, the market for power supplies of this level just doesn't use the fan type as a discriminator. They use ripple, efficiency and so on.

    I trust that you won't be coming back to this several years down the line and shall therefore assume I win the argument. Victory!
  • austinsguitar - Saturday, August 25, 2018 - link

    the fan is ball bearing?
  • Batmeat - Wednesday, August 22, 2018 - link

    Third paragraph had the word "bifurcated" in it back to back.
  • Ryan Smith - Wednesday, August 22, 2018 - link

  • mgabee - Thursday, August 23, 2018 - link

    Best PSU, beside the EVGA G3 series of course. Jonnyguru makes Corsair PSUs more brilliant with this 2018 upgrade. I have the RM550x: the quality is insane, deadly silent, Vcore drop halved under load. It is definitely a 10yr long PSU with the best price/performance ratio.
  • IgorM - Thursday, August 23, 2018 - link

    I must disagree with crypto mining part. We have at least 3 Rmx 850 and at least 20 Rmx 1000 working almost a year with pretty harsh conditions, up to 43 C in the room, almost full load, and none died yet and works excellent. We also have LC power PSUs, because supply of Corsair was limited at the time, and they are dying often.

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