triplesixohemgee

killert

Quote: Originally Posted by triplesixohemgee the CPU is a 3 pin connector and not a 4 pin.

What do you mean? got a picture?

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triplesixohemgee

Pictures to be posted after I return from Father's Day Dinner.

Joe88

you mean the power connector?

I think your looking at the cpu fan power conenctor

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OnyxIce

Well, it depends, I imagine you're talking about the fan? I'm using a 3-pin CPU (fan) connector on a 4-pin connector (on the mobo) and it's all working fine..?

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Joe88

the 4th pin is used to control the fan RPM on certain boards
if the CPU temps go above a set limit the board will automatically raise the RPM of the CPU fan to cool it down, even while playing a game
almost all AMD systems where only 3 pins

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tetrafluoroethane

The 4th wire is used by certain ECM (Electronically Commutated Motor) fans to control speed. I think it takes a stream of pulses at about 25kHz with the low duty cycle determining speed, but some ECM motors are different. A 4 wire ECM fan will ramp up to full speed if the control wire is disconnected. A 3 wire ECM fan will have a probe in the airflow to sense air temperature and air velocity. (There might be a 3 wire ECM fan that uses one wire for bidirectional communication, but I have not seen one.)
If a regular 3 wire fan is used where a 4 wire ECM fan should be used, it will simply operate at full speed, without any of the advantages of ECM. (Some boards might expect an ECM fan and falsely indicate fan failure.) A 3 wire ECM fan will use its internal sensor to regulate speed, which may or may not be a problem.

Note that ECM fans use less power than regular fans of the same size and CFM, so a regular fan can overload the port in some cases. Generally not a problem, however.

BTW, an ECM fan works by using a microprocessor-controlled inverter to turn DC into 3 phase AC and then running a miniature 3 phase motor from the inverter output. 3 phase motors are powerful, efficient, and quiet compared to single phase and DC motors, which makes them particularly useful in cooling fans.