I have an Gigabyte H55M-S2V motherboard and it has a 4 pin cpu fan connection. I didn't realize when I purchased a ISGC-400 cpu cooler from Thermaltake that it only has 3 pins to connect to the motherboard. It's all setup and apparently working fine so what is that 4th pin for? If anyone can shed some light on this I would appreciate it!Mark

I think its for fan control

I think its for fan control

It is indeed.I had the same issue with my Noctua NH-U12P SE2. Plugging in three pins just means the CPU fan will be at full speed all the time. Not really a problem if you have a nice quiet fan on your aftermarket cooler. I have two Noctua NF-P12s running at full speed and can hardly hear them.If it makes too much noise, it is possible to get bridging leads with in-line resistors to wind the fan speed down.

Thanks Guys! I didn't realize it because when I looked in the BIOS, I saw that the CPU Fan speed was adjusting itself. I suppose it was just reading the voltages it was passing to the motherboard connector and displaying the estimated fan speed if I had a 4 pin connector on my cooler.Thanks again...Mark