Asus RS520-X5/PS8 - Manual (Page 48)

4-6 Chapter 4: Motherboard information
4. LAN controller setting (3-pin LAN_EN1)
This jumper allows you to enable or disable the onboard Intel ® 82563EB
Gigabit LAN controller. Set to pins 1-2 to activate the Gigabit LAN feature.
5. Fan control setting (3-pin FAN_SEL1)
This jumper allows you to switch for fan pin selection Set to pins 1-2 for 4-pin
fans or pins 2-3 for 3-pin fans.
• If you use a 4-pin fan but set the jumper to pin 2-3, the fan you installed
may not work.
• If you use a 3-pin fan but set the jumper for a 4-pin fan, the fan controll will
not work and the fan you installed will always run at full speed.