Cooler Master UCP Ultimate 900W PSU

Results

The Cooler Master UCP 900W is quite simply excellent. Only one voltage: 12V #1 at 100 percent load dipped slightly, but remained well within ATX spec, and every other voltage is solidly in the green.

The efficiency is chart-toppingly good - nearly reaching 90 percent at full load, and averaging well over 88 percent in all but 20 percent load where it dips to just over 82 percent. The PFC here did drop below 90 percent too and both of these factors together technically make it fail the Silver 80 Plus spec, however the high load scores also greatly exceed it.

Cooler Master's four rail design is pretty good - dedicating rails three and four to PCI-Express, and splitting one and two between SATA, Molex, ATX and EPS 12V power connectors. In this way the load is evenly balanced across the major current users, however the total 852W available on the 12V has to be used everywhere, unlike a single rail design where it can be used anywhere. Cool Master could do a single rail design, like the Silent Pro series, because of the single 12V AC-DC converter, but it chooses to split it instead.

Noise-wise, the unit is very, very quiet at 20 and 50 percent loads and remained very cool running too. At 75 percent load there is still no fan noise, while the airflow gets a bit warmer but the unit stays cool to touch. At full load the fan noise rises from very quiet to noticeable, but very tolerable. Most of the noise is the generation of airflow rather than fan spinning and the sides and base are now warm while the airflow out of the back is quite warm-hot.