Asus Rampage III Black Edition - Manual (Page 68)

5. Digital audio connector (4-1 pin SPDIF_OUT)
This connector is for an additional Sony/Philips Digital Interface (S/PDIF)
port(s). Connect the S/PDIF Out module cable to this connector, then install
the module to a slot opening at the back of the system chassis.
The S/PDIF module is purchased separately.
4. USB 3.0 connector (20-1 pin USB3_910)
This connector is for the additional USB 3.0 ports, and complies with the USB
3.0 specificaton that supports up to 4.8 Gbps connection speed. If the USB
3.0 front panel cable is available from your system chassis, with this USB 3.0
connector, you can have a front panel USB 3.0 solution.
You can connect the ASUS front panel USB 3.0 box to this connector to obtain
the front panel USB 3.0 solution.
2-36 Chapter 2: Hardware information