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Cooler Master RealPower M850 (RS-850-ESBA)

The next model to be discussed is more typical in terms of its design. It is cooled by a 135mm fan as has become de facto standard for medium and high-wattage power supplies.

I want to note that Cooler Master offers two 850-watt RealPower series models. One has fixed cables and another has modular cables. I will be talking about the modular version.

The PSU comes in a large white box with a carry handle.

Exterior Design

The PSU looks ordinary enough. The only interesting thing in its appearance is that its front panel is “transparent” for the air. It is all perforated save for the zone with a mains connector and an On/Off indicator.

There are six connectors for peripheral power cables and four for graphics cards, which is more than the above-discussed Antec TruePower Quattro offers. You cannot confuse connectors as they are shaped differently.

Interior Design

Removing the cover, I could instantly tell the real manufacturer of this power supply. It is Enhance. This PSU has two power transformers working in parallel, an active PFC device, and dedicated voltage regulation based on magnetic amplifiers. As is typical of Enhance products, the quality of assembly is very high.

There are Teapo capacitors at the PSU’s output. Teapo is a respectable brand.


This PSU has as many as six “virtual” +12V lines rated for a max current of 28 A (the graphics card lines) or 18 A (the rest of the lines). This abundance of power lines allows distributing the load without worrying that one particular line might overload the whole PSU (such an unpleasant thing occurs when the overload protection of a PSU with virtual output lines is triggered by an exceedingly high current on any particular line whereas the total PSU load is yet far from maximum). Well, PSUs that have no splitting of the +12V rail into multiple lines have no such problem at all.

Cables and Connectors

The PSU is equipped with the following cables and connectors:

  • Mainboard cable with a 24-pin connector (50 cm)
  • One CPU cable with a 4-pin connector (65 cm)
  • One CPU cable with an 8-pin connector (65 cm)
  • Four connectors for graphics card cables
  • Six connectors for peripheral power cables

Included with the PSU are:

  • Two graphics card cables with one 6-pin connector on each (50 cm)
  • Two graphics card cables with one 8-pin connector on each (50 cm)
  • Two cables with two PATA power connectors and one floppy-drive plug on each (50+15+15 cm)
  • Two cables with three PATA power connectors on each (50+15+15 cm)
  • Two cables with four SATA power connectors on each (50+15+15+15 cm)

This selection of cables and connectors looks good, yet not perfect to my taste. First, the fixed 4-pin CPU connector on a separate cable won’t be needed by a majority of users because they will instead use the fixed 8-pin one. Mainboards with both power connectors are rather rare (server boards, mostly). Second, I would prefer four SATA power cables, even with fewer connectors on each, to the included two because one cable usually goes to the optical drive and does not reach to the HDDs.

UPS Compatibility

Working with my APC SmartUPS SC 620, this power supply was stable at loads up to 366 W when powered by the mains and up to 335 W when powered by the batteries. They had no problems switching to the UPS’s batteries.

Output Voltage Stability


The PSU was not stable when the load on the +3.3V rail was low (below 1 A). Otherwise, there were no problems: every voltage deflects no more than 3% from its nominal value.

Output Voltage Ripple


The output voltage ripple is within the norm on every of the three main power rails at full load.


The PSU is cooled by a 135x135x25mm fan from Young Lin Tech Co.


The fan’s speed is constant and below 900 RPM at loads up to 500 watts. It begins to rise at higher loads, reaching a maximum of 1450 RPM. The PSU would be very quiet if it were not for the rumbling sound the fan of my sample produced even at low speeds. However, I have seen a lot of PSUs with YLTC fans that had no such problems (including PSUs manufactured by Enhance), so I have no doubts that this is a problem of the specific sample of the fan.

Efficiency and Power Factor


The PSU is over 80% efficient, reaching a maximum of 88%. It is 82.5% efficient at full load.

Standby Source


The standby source is rated for a current up to 3.5 A. Its voltage sags to 4.9 V under full load, the permissible minimum being 4.75 V.


I have seen a number of high-quality power supplies from Cooler Master and the RealPower M850 can now be counted among them. It is a modular PSU with a handy selection of cables, good electrical parameters and low fan speed. I have to confess that my sample of the PSU had a defective fan, but practice suggests that no maker can guarantee the lack of such defects.

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