Asus P5K - Manual (Page 51)

ASUS P5K 2-27
12. USB 2.0 ports 3 and 4. These two 4-pin Universal Serial Bus (USB) ports
are available for connecting USB 2.0 devices.
13. Coaxial S/PDIF Out port. This port connects an external audio output device
via a coaxial S/PDIF cable.
14. USB 2.0 ports 5 and 6. These two 4-pin Universal Serial Bus (USB) ports
are available for connecting USB 2.0 devices.