Asus P4-P5N9300 - Manual (Page 41)

3-9 ASUS P2-P5N9300/P4-P5N9300
7. 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.
8. USB connectors (10-1 pin USB56, USB78)
These connectors are for USB 2.0 ports. Connect the USB module cable
to any of these connectors, then install the module to a slot opening at the
back of the system chassis. These USB connectors comply with USB 2.0
specification that supports up to 480 Mbps connection speed.
Never connect a 1394 cable to the USB connectors. Doing so will damage the
motherboard!
The USB module is purchased separately.