User`s manual

2-10 Chapter 2
(11). CD1, AUX1: Internal Audio Connector
These connectors connect to the audio output of internal CD-ROM drive or add-on card.
U23: POST Code Display (12).
This is an LED device to display the “POST” Code, the acronym of Power On Self Test. The computer
will execute the POST action whenever you power on the computer. The POST process is controlled by
the BIOS. It is used to detect the status of the computer’s main components and peripherals. Each POST
Code corresponds to different checkpoints that are also defined by the BIOS in advance. For example,
“memory presence test” is an important checkpoint and its POST Code is “C1”. When the BIOS executes
any POST item, it will write the corresponding POST Code into the address 80h. If the POST passes, the
BIOS will process the next POST item and write the next POST Code into the address 80h. If the POST
fails, we can check the POST Code in address 80h to find out where the problem lies.
IT7-MAX2