4-pin fans are PWM fans. the first 3 pins/wires are the same as a standard 3-pin fan, the 4th pin/wire is the 'pulse' wire for PWM speed control. you can plug a 4-pin fan into a 3-pin motherboard fan header, but speed control will be lost. depending on the fan, some will run at maximum speed, others will run at minimum speed.
you can also use a 3-pin fan with a 4-pin motherboard fan header. same as above the first 3 pins/wires are the same as a standard 3-pin motherboard fan header, the 4th pin is the 'pulse' wire for PWN speed control. using a 3-pin fan poses no danger or loss of functionality. it will simply run at full speed, just as it would if it were plugged into a standard 3-pin motherboard fan header.
both '4-pin' examples above are in reference to a 4-pin PWM fan connector (looks just like a regular 3-pin fan connector but with an extra pin/wire). some fans have a 4-pin molex connector (same power connector used for PATA hard drives and CD/DVD drives). these connectors do not plug into the motherboard, but directly into the power supply. even though the connector has 4 pins, only 2 of them are actually used. this type is equivalent to a 2-pin fan connector and should not be confused with a 4-pin PWM connector.
NOTE: the 2 pictures used above were taken from
www.intel.com
DeepMartin said:
i just plugged a two cable fan to the 2nd system fan mobo now i wonder if its a big no no
cuz now m thinking without the third cable the mobo has no control of the speed of the fan right?
wrong. the third wire (usually yellow) on a 3-pin fan connector is only to monitor fan speed (it doesn't control fan speed, it only monitors it). the other two wires (usually red and black) are the same as a 2-pin fan connector. you can use a 2-pin fan with a 3-pin or 4-pin motherboard fan header as long as they are connected to the proper two pins (+12v and ground).
:wave: