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Old October 7, 2011, 04:57 PM
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Arinoth Arinoth is offline
Join Date: May 2009
Location: Halifax
Posts: 9,158

Yep, that fourth pin is actually the PWM (Pulse-Width Modulation) wire, essentially it allows the computer to control how fast the fan speed is without altering the amount of voltage delivered to it. 3 pin fans can only have their fan speeds changed by changing the voltage delivered to it.
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