What is the difference between the CPU_FAN and CPU_OPT pins on the motherboard? I am installing 2 PWM fans as part of an H100 CPU cooler, so would I connect 1 to CPU_FAN and 1 to CPU_OPT, or do I need to connect them both to CPU_FAN with a Y-cable?
CPU_FAN is the primary header and CPU_OPT the secondary. Meaning the CPU_FAN signals to the BIOS that there 'is' an operating fan to cool the CPU and it also signals the 'fan' to increase it's fan speed to offset the CPU Temperatures; i.e. is signals the H100 to increase or lower the fans speed.
Installing the H100 it's best to:
* CPU_FAN - single wire from H100
* 4-Pin Molex (from PSU) to H100 pump; power for both the pump and fans 2 or 4.
* Use the H100's 4-port headers for fans.
That is what I thought, but I have read mixed results about certain fans not changing speeds (or not spinning up at all) when connected to the H100. I guess I will test it out and see what happens. Thanks.
Again, the H100 should be fine and it's controller supports both 3-pin & 4-pin fans (PWM). The only issues are low RPM and low static pressure fans; the NoiseBlocker M12-P appears to be a 4-pin and 43-87 CFM but 29dBA is loud...