Chapter 4 34
This chapter provides instructions on how to troubleshoot system hardware problems.
Hardware Diagnostic Procedure
Please refer to generic troubleshooting guide for troubleshooting information relating to following topics:
qPower-On Self-Test (POST)
qPOST Error Messages List
qError Symptoms List
qUndetermined Problems
Power-On Self-Test (POST)
Each time you turn on the system, the Power-on Self Test (POST) is initiated. Several items are tested during
POST, but is for the most part transparent to the user.
The Power-On Self Test (POST) is a BIOS procedure that boots the system, initializes and diagnoses the
system components, and controls the operation of the power-on password option. If POST discovers errors in
system operations at power-on, it displays error messages on screen, generates a check point code at port
80h or even halts the system if the error is fatal.
The main components on the main board that must be diagnosed and/or initialized by POST to ensure system
functionality are as follows:
qMicroprocessor with built-in numeric co-processor and cache memory subsystem
qDirect Memory Access (DMA) controller
qInterrupt system
qThree programmable timers
qROM subsystem
qRAM subsystem
qCMOS RAM subsystem and real time clock/calendar with battery backup
qOnboard parallel interface controller
qEmbedded hard disk interface and one diskette drive interface
qKeyboard and auxiliary device controllers
q1.44M floppy controller
qI/O ports
qOne parallel port
qOne PS/2-compatible mouse port
qOne PS/2-compatible keyboard port
NOTE: When Post executes a task, it uses a series of preset numbers called check points to belatched atport
80h, indicating the stages it is currently running. This latch can be read and shown on a debug
board.The following table describes the BIOS common tasks carried out by POST. Each task is denoted
by an unique check point number. For other unique check point numbers that are not listed in the table,
refer to the corresponding product service guide.
System Troubleshooting