2.1 Power-On Self-Test (POST)
The power-on self-test (POST) is a series of system tests that verify the
correct operation of the base system and most options. The POST runs each
time the system is powered-on. It compares the system configuration
information it detects with the configuration stored in the CMOS RAM. The
test takes up to 90 seconds to finish, depending on the options installed.
The POST can detect critical and noncritical errors in the following
areas:
System board
Memory
VGA
Keyboard
Diskette drives
Fixed disk drives
Serial port
Parallel port.
Some adapters have Read Only Memory (ROM) modules that contain extended
BIOS routines that work with the system POST.
To start the POST, power-on the system. The following happens:
The keyboard status lights blink on, then off.
While the memory is being tested, the memory size appears in the top
left corner of the screen in 64KB increments.
When the POST is successful, one short beep occurs.
If an operating system is not automatically loaded from a fixed disk
drive and a diskette is not present in drive A, the diskette prompt is
displayed along with the F1 prompt. The diskette and F1 prompts are
icons showing that a diskette should be inserted into diskette drive
A. Press the F1 key to continue loading programs from the diskette.
PICTURE 2
If POST errors are displayed, the F1 key can be pressed to bypass the
errors and allow the POST to attempt to complete. Depending on the error,
the POST may or may not complete.
If the Reference Diskette is present in drive A when a POST error is
detected, the system displays the POST error message along with a message
generated from the Reference Diskette. This additional message instructs
the user to take a specific action to solve the problem. The message is
not intended for use by trained service personnel.
IBM HMR Diagnostics for Micro Channel
Power-On Self-Test (POST)
¦ Copyright IBM Corp. 1990
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