I checked the PSU out with an APC SmartUPS SC 620, and the UPS’ indicator would report overload at a load of over 365W and 330W when working from the mains and batteries, respectively. Switching to the batteries was performed without problems.
There’s almost no pulsation on the +5V rail at a load of 600W – you can only see small narrow spikes at the moments of switching the inverter’s transistors. At the same load, the voltage ripple was 26 millivolts on the +12V rail and 10 millivolts on the +3.3V rail. There’s only high-frequency pulsation here.
The cross-load characteristics of this PSU look splendid. I’d want to draw your attention to this power supply’s ability to yield nearly full power across the +12V rail only. The +5V voltage is the only one to get near the maximum permissible deflection (red color), but only at those loads that have little to do with modern computers.
The PSU employs an Adda AD1212HB-A71GL fan whose speed is regulated linearly in most of the load range (from 150 to 450W). The PSU is almost silent at low loads (a fan speed of less than 800rpm) and is quiet at high loads. Although the fan speed is set up with some reserve (the air coming out of the PSU at full load of 600W feels just barely warm), it is lower than that of many other products (e.g. of the above-described CoolerMaster iGreen Power). The use of high-quality fans from Adda contributes to the PSU’s quietness, too. But running a little ahead, I should confess that the Corsair is not the quietest PSU on the market. S-12 series models selling under Seasonic’s own brand are quieter still. On the other hand, the CMPSU-620HX is going to satisfy a vast majority of users with its noise characteristics, too.
The PSU efficiency is 85% at the maximum and 84% at full load. That’s a very good result, quite accurately coinciding with the specification. The power factor is 0.99 on average.
Corsair Memory has made a successful debut on the PSU market. The CMPSU-620HX doesn’t have any apparent drawbacks. It is a high-wattage model with excellent parameters, particularly very quiet at work. If its 620W wattage is excessive for your system (I guess it is excessive for a majority of today’s PCs), you may want to consider its 520W analog, the CMPSU-520HX model.