how are PC fans controlled?

[38034580]

Is the control pin pulled high and floating, low and floating, or high and low?

[mariushm]

How many questions are you gonna ask without doing the minimum of research? 

 

intel  fan specification pdf : https://www.google.com/search?q=intel+fan+specification+pdf

 

First result is this : 4_Wire_PWM_Spec.pdf

 

Also, it doesn't matter.   You can control by adjusting voltage or by limiting current, if you don't have the 4th pwm wire. 

 

Also, figure out what you want to do, gather your questions, make a longer post / thread. Explain what you're trying to do.. because out of context people may give you some answers that won't apply to you, or you're asking the wrong questions and other easier solutions may be available.