Performance

The UL number E166947 reveals that the PSU is made by OEM manufacturer Enhance Electronics for Cooler Master.

Cooler Master RealPower M850 850W, RS-850-ESBA
AC Input	100V-240V, 6.3-12A max., 50-60 Hz
DC Voltage	+3.3V	+5V	+12V1	+12V2	+12V3	+12V4	+12V5	+12V6	+5VSB
Max. Output	25A	30A	18A	18A	28A	28A	18A	18A	3.5A
	191W		768W						17.5W
	850W

Tested on: AMD Athlon64 FX-62 @ 2800 MHz, ABIT AT8, 2x 512 MB DDR400, WD Raptor 36 GB, Radeon X1900 XTX + Radeon X1900 XTX Crossfire

While the 12V line is very stable, the 3.3V and 5V lines fluctuate quite a bit under load. All voltages remain within the limits of the ATX specification however, so there is nothing to worry.


The ripple voltage is exceptionally small with only 6 mV, which is one of the best results I've seen so far.

Standard deviation 3.3V	9.07
Standard deviation 5V	4.48
Standard deviation 12V	6.48
Power Factor	1.00
Ripple Voltage 12V	6.0 mV
Power Efficiency	83.6% (353W:422W)

For easier comparison between power supplies we put the (normalized) line regulation standard deviation into graphs.



Standard deviation is a statistical term, which tells how far away from the average the measurements are. In other words it's the average of the average.
A large standard deviation indicates that the data points are far from the average and a small standard deviation indicates that they are close within the average.
So the smaller the standard deviation is, the better the line regulation.