DB9M SERIAL ADD-A-PORT ADAPTER WITH BRACKET and 16in CABLE for INTEL MOTHERBOARDS Ensure smooth data flow from either your serial or parallel port with an I/O Add-a-Port Adapter Cable from Cables To Go. Choose DB9-pin or DB25-pin male serial ports. These adapter cables connect to the motherboard or I/O adapter via flat ribbon cabling, and attach to a port knockout on your computer case.