We were really impressed by this power supply. It could not only deliver 850 W at 50º C like the manufacturer says, but we could easily pull 1,000 W from it. Cooler Master could easily label this power supply as being a 1,000 W unit, but they decided to play it safe and label it as an 850 W unit, probably because efficiency drops below 80% when you pull 1,000 W.
Inside the unit all rectifiers are way overspec’ed and this explains why this power supply can easily deliver more power than labeled.
This unit is clearly targeted to someone building the ultimate gaming machine with three or four video cards, a very high end CPU and several hard disk drives.
What is good about this power supply is that it offers six virtual rails and each video card power cable is connected to a different rail. The usual configuration on other power supplies with four video card power cables is connecting two cables on one rail and the other two on another rail. If you install two power-hungry video cards on the same rail, the over current protection may kick in shutting down the power supply even if the video cards are just running inside their specs. To prevent this from happening some manufacturers simply disable the OCP circuit (transforming the power supply into a single-rail design) or configure OCP with a value that is too high. In both cases the power supply isn’t offering any kind of over current protection.
This Cooler Master unit solves this issue by putting each video card power cable on an individual rail, so the power supply won’t shut down if you are running up to four video cards inside their specs but will provide you with over current protection in case something wrong happens.
During our tests this power supply kept a very low ripple and noise levels, far below the maximum allowed levels. Voltage regulation was also perfect. Efficiency was always above 81%, being on the 87%-88% range if you pull less than 520 W from this unit.
Its fan is very quiet and this power runs very cool – its housing was only 2-3º C above room temperature.
The only “problem” you may have with this power supply is regarding its over temperature protection (OTP). Apparently the thermal sensor is only read when you turn the power supply on. If the secondary heatsink is above 60º C the power supply won’t turn on. So if you turn your PC off and then try to turn it back on and it doesn’t come back to life, wait a few minutes until the power supply cools down. We think that a LED indicating that OTP is active would be a great idea, because users may become desperate thinking that they have burned their power supply. At least we did.
The price is right for a product on the 850 W range. Just be careful because at Newegg.com this unit is quoted at USD 200 but you can find it costing less.
You also get a 5-year warranty (on the product manual it is written that this product has a three-year warranty, but the manual is wrong).
Even though this power supply delivers what the manufacturer promises, it may explode if you keep pulling 1,000 W from it continuously. Because of that we think the manufacturer should have configured over power protection (OPP) at a lower level, in order to prevent this from happening. The side effect is that you couldn’t peak 1,000 W with it, but at least you would have a safer product. That is the only reason we are not giving it our Golden Award seal, but our Silver Award. But don’t get us wrong: this is a very good product that provides a terrific cost/benefit ratio for users looking for a very high-end power supply.
