Thanks for the replies
@Dark Mantis
They're just basic 500~1400rpm 120mm 12V fans with 3-pin and 4-pin connectors. I don't really want to have to spend another £50 on a fancy fan controller just so I can slow them down from running at 100% all the time.
@Gloup_Gloup
Speedfan can only seemingly control my CPU fan and not my case fans, but it's reporting the speeds of them just fine. I'm not having trouble with that. My fans do not have any hardware controls with sliders or buttons or anything. CPU smart fan control is enabled and set to PWM, but as far as I'm aware, that is only relevant to my CPU fan and not the rest of the fan headers.
Is the P67A-UD3P simply unable to control power to the system fan headers despite them being 3-pin? n the bios it only reports the RPM of the fans, not giving any options to control them. The only control option seems to be for the CPU fan itself which is 4-pin. I've tried using the other 4-pin header on the motherboard for my akasa apache but the fan slows down and stops randomly when connected to it, even when the PC is under load.
The specific fans I'm using are:
Arctic Cooling F12 120mm PWM 3-pin (connected to pwr_fan header (3-pin))
Akasa Apache 120mm PWM 4-pin (connected to sys_fan1 header (3-pin))