The cooling fan is the same 120mm ADDA that we saw in the past Seasonic review as well. This fan is temperature controlled - meaning it will only spin as fast as required to properly cool the power supply at whatever temperature it's currently operating at. This will help to keep noise levels as low as possible and since it's an 80Plus rated power supply, this means really low! At full speed, this fan is rated at 61CFM. The fan vents out a honeycomb shaped grill in the back of the power supply.

 
(Click to enlarge)

As with the S12II, the M12II also has active power factor correction (Active PFC you may know this term as). This ensures that your computer will get the "cleanest" power possible by helping to reduce line loss and power distortion that may occur on the way into the supply from your wall. In addition to that you also have over power, over voltage and short circuit protection to keep your system safe at all times.

Installation:
Installation of the M12II was a breeze and I did not encounter any problems along the way.

Testing:
The system the M12II will be tested on is listed below.

Testing System:
CPU: AMD Athlon 64 3200+ (Socket 939) @ stock speeds
Motherboard: Biostar NF4UL-A9
Memory: 1gb (4x256mb) PC3200 400mhz
HDD: Western Digital 160gb SATA II (WD1600JS), Seagate 250gb SATA II
Video: Asus EN7600GS Silent
Sound: Mackie Onyx Satellite Firewire Audio Interface
Power Supply: Seasonic M12II 500W
OS: Microsoft Windows XP Professional SP2

To test the M12II I will use the same method I use for all power supply reviews. First, the idle voltages will be taken and then after running the system at 100% load for 30 minutes I will record the load voltages. These results are seen in the graph below:

I was surprised to see that even under such heavy load that my system was only able to give a slight nudge to the +12V rail's voltage. The +5V and +3V voltages were dead on under idle conditions and amazingly were able to maintain that performance even under heavy load for a long period of time. Some people question why Seasonic doesn't make these power supplies in wattages higher than 500W. When it comes down to it, quality is the answer. A "well built" 500W power supply could easily outperform a cheap-o 800W+ power supply on any day. As you saw with my test results, my system wasn't even able to budge the voltages on the M12II, meaning it can still take a heck of a lot more! This is impressive when you compare it to the fact we've reviewed some 800W+ power supplies in the past where my system has been able fluctuate the voltages quite a bit, even on some past 500W model reviews for other manufacturers!

Throughout all my testing of the M12II I was glad to see that it's kept the same noise levels at the S12II - I mean lack-of noise levels! In my system at about 1m away I could not hear the M12II in operation, even when the system was under full load for a while. The only noticeable way to hear the M12II over my other components was to put my ear right up to it and even then the only sound I could hear was the sound of the quiet motor and some airflow. This is truly the signs of a high quality 80Plus power supply in action!