Fans speed?

[makaveli2007]

hi guys

about the fans with 3 connectors & these with 4 connectors

the ones with 3 connectors can send RPM signal to the MOBO , but wont recive a orders from the MOBO

the ones withe 4 connectors sends & recives RPM signals from the MOBO?

 

[danny2000]

http://pcbheaven.com/wikipages/How_PC_Fans_Work/

 

[13thmonkey]

no, 3 connectors can (if the mobo is set up), send a varied voltage to affect speed, and the rpm tells the mobo what it is doing
4 pins can do the above and send a digitised variable voltage (pulse width modulation) to vary the speed.