Asus Crosshair IV Formula - Manual (Page 63)

9. OC Station connector (8-pin OC_STATION)
This connector is for ASUS OC Station connection only. Connect one end
of the supplied data cable to the GP connector on the OC Station and the
other end to this connector and USB13 on the motherboard to enjoy easier
overclocking.
8. 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.
ROG Crosshair IV Formula 2-37