EfficiencyUsing the efficiency results from the previous page, we plotted a chart showing the RM750's efficiency at low loads and loads equal to 20%-110% of the PSU's maximum-rated load.
Thanks to its good design with four mosfets in total acting as main switchers, the RM750 is able to catch up with the older Golden SuperFlower platform sporting high overall efficiency by utilizing a more sophisticated design with an LLC resonant converter.
Efficiency at Low LoadsThe next tests measure the efficiency of the RM750 at loads much lower than 20% of its maximum-rated load (the lowest load the 80 Plus Standard measures). The loads we dialed were 40 W, 60 W, 80 W, 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 at Low Loads |
|Test #||12 V||5 V||3.3 V||5 VSB||Power|
|Efficiency||Fan Speed||Fan Noise||PF/AC |
|1||1.834A||1.972A||1.955A||0.196A||39.73W||76.61%||0 RPM||0 dBA||0.669|
|2||3.410A||1.973A||1.955A||0.390A||59.73W||81.73%||0 RPM||0 dBA||0.763|
|3||4.984A||1.973A||1.955A||0.588A||79.70W||84.88%||0 RPM||0 dBA||0.825|
|4||6.562A||1.973A||1.955A||0.785A||99.69W||86.85%||0 RPM||0 dBA||0.865|
The fan never spun up at low loads and registered efficiency was very good since it easily cracked the 80% mark in three out of the four tests. It was even above 75% with 40% load. Other 750 W units only reached 70% efficiency under those conditions.
Corsair Link ScreenshotsWe took some screenshots of the Corsair Link software during the above tests. The order of screenshots is the same as the order of tests in the above table (test#1 to #4).
5VSB EfficiencyThe ATX spec states that 5VSB standby supply 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.
| 5VSB Efficiency|
|Test #||5VSB||Power (DC/AC)||Efficiency||PF/AC Volts|
Efficiency on the 5VSB rail was average and dropped a little more at full load, which is indicative of 3 A being very close to the limits of this rail.
Power Consumption in Idle & StandbyIn 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).
| Idle / Standby |
|Mode||12 V||5 V||3.3 V||5VSB||Power (AC)||PF/AC Volts|
Phantom power is, like its 850 W sibling, very low, close to one fifth of the limit the ErP Lot 6 2013 directive sets (0.5 W).
Fan RPM, Delta Temperature & Output NoiseThe 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 39°C-45°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). Background noise inside the anechoic chamber was below 30 dBA during testing, and the results were obtained with the PSU operating at 39°C-45°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 temperature was between 28°C and 30°C in this case.
This is one of the quietest PSUs we have ever tested. The fan will be sitting idle most of the time if installed into a case with good airflow, so make sure to install the unit with the fan grill facing up to give hot air a way out of the PSU.