I don't understand why Chassis3 and CPU_OPT have a bios setting, but Chassis 1/2 don't. I couldn't figure out why my computer sounded like a helicopter until I started moving things around. The product description states that both 3-pin and 4-pin fans can be controlled, but the autodetection itself seems like it was causing problems with fan control (I also had two fans into a splitter and this refused to be controlled no matter what). I had to move my Fan Hub away from the chassis1 header and move it to the CPU_OPT Header since none of the others would allow me to control the hub.