Asus P7H55-M PRO - Manual (Page 50)

2-30 Chapter 2: Hardware information
Chapter 2
3. USB connectors (10-1 pin USB78; USB910; USB1112)
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!
4. Serial port connector (10-1 pin COM1)
This connector is for a serial (COM) port. Connect the serial port module cable to this
connector, then install the module to a slot opening at the back of the system chassis.
The COM module is purchased separately.
The USB module is purchased separately.