Asus RS500A-S6/PS4 - Manual (Page 54)

4-6 Chapter 4: Motherboard information
5. DDR3 voltage control setting (4-pin LVDDR3_SEL1; LVDDR3_SEL2)
These jumpers allow you to adjust the DIMM voltage. Set to pins 1–2 to
select 1.5V BIOS control, pins 2–3 to select 1.2V Force or 3–4 to select
1.35V Force.
4. LAN controller setting (3-pin LAN_SW1)
This jumper allows you to enable or disable the onboard Intel ® Gigabit LAN
controller. Set to pins 1-2 to activate the Gigabit LAN feature.