Nvidia nForce 550 MCP User Manual page 23

(11) SPDIF In/Out Header: SPDIF In/SPDIF Out
The SPDIF output is capable of providing digital audio to external speakers or
compressed AC3 data to an external Dolby digital decoder. Use this feature only when
your stereo system has digital input function. Use SPDIF IN feature only when your
device has digital output function
(12) Serial COM Port: COM1
COM1 are the 9-pin block pin-header. The On-board serial port can be disabled through
BIOS SETUP. Please refer to Chapter 3 "INTEGRATED PERIPHERALS SETUP" section
for more detail information
(13) Parallel Port Header (25-pin male): PARALLEL
The On-board Parallel Port can be disabled through the BIOS SETUP. Please refer to
Chapter 3 "INTEGRATED PERIPHERALS SETUP" section for more detail
information.
(14) IEEE1394a Port : 1394A / 1394B （Optional）
Pin1
Serial COM Port 9-pin Block
Pin 1
.
PARALLEL Connector
Pin 1
1394A
Pin 1
1394 Port Headers
i25
1394B