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The manual does not show details for that. I am in the habit of not merely pressing that key I hold it down until the BIOS Setup opening screen (p.40) appears. It says when you start up the system, press the "Del" key. On p.33 of your manual it says you can make this setting for EACH of the headers you are using by accessing the correct BIOS Setup screens. To control their speeds your mobo header they are plugged into MUST be configured to use the older Voltage Control Mode (aka DC Mode) and NOT the newer PWM Mode. I am pretty sure each has THREE wires from it (Red, Black and Yellow), and they end in a connector with THREE holes. Look at the wires from each of your four fans.
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