Asus P4-P5N9300 - Manual (Page 37)

3-5 ASUS P2-P5N9300/P4-P5N9300
4. FAN_PWR_SEL (3-pin FAN_PWR_SEL)
Set this jumper to pins 1-2 if you are using a 4-pin CPU fan. Set this
jumper to pins 2-3 if you are using a 3-pin CPU fan.
3. Keyboard power (3-pin KBPWR)
This jumper allows you to enable or disable the keyboard wake-up feature.
Set this jumper to pins 2-3 (+5VSB) to wake up the computer by pressing
a key on the keyboard (the default is the Space Bar). This feature requires
an ATX power supply that can supply at least 1A on the +5VSB lead, and a
corresponding setting in the BIOS.