This fan/s spins at 1200 plus rpm all the time, since its power pin plug is different than the motherboard controlled pin, so you hook it up to the chassis pin which is not controlled, thus the constant rpm of 1200 or so. The problem is that the mother board has two settings which can create a error, causing a problem i had that will not allow booting to windows after post. The mother board detects that the fan/s are spinning in excess of its prescribed 600 rpm minimum and lists it interally as a fault or error. There is another MB feature in booting advanced which if it detects an error it will stall the booting to windows and mandate you hit F1 to proceed to bios. This forces you to deal with the error or fault, which is good. Sooo, in the monitor section of bios "Disable" Chassis Q-Fan control and more important "Ignore" CPU Fan Speed Low Limit. This will permit Bios to allow the Noctura D14 to spin at its regular 1200 rpm without creating an internal error, which will allow booting to windows as normal. Sorry for the rant, but this problem was haunting me for a few days without a solution and hopefully will save some time for the next noob like me.