Efficiency

Using the efficiency results from the previous page, we plotted a chart showing efficiency of the RM850 at low loads and at loads equal to 20%-110% of the PSU's maximum-rated load.



The unit's performance was close to what we expect from a Gold PSU, with both low and normal loads. The above charts nicely show that its performance isn't too far away from that of its Platinum siblings, which proves this platform to have potential. However, Corsair's Platinum units register much tighter voltage regulation on all rails, which is the price the RM850 PSU pays to provide its high efficiency. But you can't really call a voltage regulation within 3% bad.

Efficiency at Low Loads

In the next tests, we measured the efficiency of the RM850 at loads much lower than 20% of its maximum-rated load (the lowest load the 80 Plus Standard measures). The loads we dialed were 40W, 60W, 80W, and 100 W (for PSUs with a capacity over 500 W). This is important for settings where the PC is in idle mode with Power Saving turned on.


Efficiency was pretty high at low loads, especially for a unit with 850 W maximum output. We even got a reading of over 75% at 40 W load, and the unit easily surpassed the 80% mark in the other three tests.

5VSB Efficiency

The ATX spec states that the 5VSB standby supply's efficiency should be as high as possible and recommends 50% or higher efficiency with 100 mA of load, 60% or higher with 250 mA of load, and 70% or higher with 1 A or more of load.

We will take four measurements: one at 100, 250, and 1000 mA each, and one with the full load the 5VSB rail can handle.


In the first two tests, 5VSB efficiency was outstanding, but the rail failed to keep its performance and fell below the 80% mark in the last two tests. Its results were then still good enough, but not ground breaking. Finally, the efficiency peak occured in test#3 and not the full load test, which is indicative of the 5VSB circuit being close to its limit at 15 W power output.

Power Consumption in Idle & Standby

In the table below, you will find the power consumption and the voltage values of all rails (except -12V) when the PSU is in idle mode (powered on but without any load on its rails) and the power consumption when the PSU is in standby mode (without any load at 5VSB).


Vampire power of this unit is among the lowest we have ever seen, which is the reason behind its outstanding 5VSB efficiency during the first two low-load tests on that rail.

Fan RPM, Delta Temperature & Output Noise

The cooling fan's speed (RPMs) and the delta difference between input and output temperature are illustrated in the following chart. The following results were obtained at 41°C-46°C ambient.



A chart that shows the cooling fan's speed (RPMs) and the output noise follows. We measure the fan's noise from 1 meter away, inside a small custom-made anechoic chamber whose internals are completely covered in specialized soundproofing material (Be Quiet! Noise Absorber Kit). The background noise inside the anechoic chamber was below 30 dBA during testing, and the results were obtained with the PSU operating at 41°C-46°C ambient.



The following graph illustrates the fan's output noise throughout the entire operating range of the PSU. The same conditions of the above graph apply to our measurements, but the ambient in this case was between 28°C and 30°C.



The V550S unit we reviewed recently did not hold the crown of quietest PSU for long, since the RM850 is the new king now. Corsair was dead serious when they stated that the RM units will operate quietly!