Intel GA-8I945P PRO - Manual (Page 43)

BIOS Setup - 43 -
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CPU Smart FAN Control
Disabled Disable this function.
Enabled When this function is enabled, CPU fan will run at different speed depending on
CPU temperature. Users can adjust the fan speed with Easy Tune based on
their requirements. (Default Value)
CPU Smart FAN Mode
This option is available only when CPU Smart FAN Control is enabled.
Auto BIOS autodetects the type of CPU fan you installed and sets the optimal CPU
Smart FAN control mode for it. (Default Value)
Voltage Set to Voltage when you use a CPU fan with a 3-pin fan power cable.
PWM Set to PWM when you use a CPU fan with a 4-pin fan power cable.
Note: In fact, the Voltage option can be used for CPU fans with 3-pin or 4-pin power cables.
However, some 4-pin CPU fan power cables are not designed following Intel 4-Wire fans PWM
control specifications. With such CPU fans, selecting PWM will not effectively reduce the fan
speed.