Power-On Self Test (POST)
POST is a series
of diagnostic tests that run automatically when the system is turned
on. After the computer is turned on, POST checks the
following assemblies to ensure that the computer system is properly
functioning:
- Keyboard
- System board
- Memory modules
- Video memory
- Diskette drives
- Hard drive
- Power supply
POST
also detects the type of mass storage devices installed in the computer.
If POST finds an error
in the system, an error condition is indicated by an audible and/or
visual message. The table below gives explanations of the error codes
and a recommended course of action.
Error
Message |
Probable
Cause |
Recommended
Action |
Diskette
Drive A Error |
Drive
A: is present, but fails the BIOS POST diskette tests. |
- Run Setup.
- Replace the signal cables.
- Replace the disk drive.
|
Extended
RAM failed at offset |
Extended
memory not working or not configured properly. |
- Replace
the memory modules.
- Replace the system
board.
|
Failing
Bits nnn |
nnn is a
map of the bits at the RAM address which failed the memory test. |
- Run Setup.
- Replace the system
board.
|
Fixed
Disk 0 or 1 |
Hard
drive is not working or not configured properly. |
- Run Setup.
- Replace the signal cable.
- Replace the hard drive.
|
Fixed
Disk Controller Failure |
Hard drive
is not working or not configured properly. |
- Run Setup.
- Replace the system
board.
|
Incorrect
Drive A Type |
Type of diskette in drive
A not correctly identified. |
- Run Setup
- Replace the disk
drive.
|
Invalid
NVRAM Media Type |
Problem with
NVRAM (CMOS) access. |
Replace the system
board.
|
Return
to top
|
Keyboard
Controller Error |
Keyboard,
I/O keyboard controller (on system board), or mouse error. |
- Replace the keyboard.
- Replace the mouse.
- Replace the system
board.
|
Keyboard
Error |
Keyboard,
I/O keyboard controller (on system board), or mouse error. |
- Replace the keyboard.
- Replace the mouse.
- Replace the system
board.
|
Operating
System not found |
Operating system cannot be located
on either drive A or C.
|
Run Setup.
|
Parity
Check 1 |
Parity error
found in the system bus. |
- Run Setup.
- Replace the memory
modules.
- Replace the system
board.
|
Parity
Check 2 |
Parity error
found in the I/O bus. |
- Run Setup.
- Replace the ISA board (modem).
|
Real
Time Clock Error |
Real-time
clock fails BIOS test. |
Replace the system
board.
|
System
Battery is Dead |
RTC
battery is dead. |
- Replace the RTC
battery.
- Run Setup.
|
Return
to top
|
System
BIOS Shadowed |
System BIOS
copied to Shadow RAM. |
Status Message: no action required.
|
System
Cache Error |
RAM cache
failed the BIOS test.
|
Run Setup.
|
System
CMOS Checksum Bad |
CMOS is corrupted
or modified incorrectly.
|
Run Setup.
|
System
RAM failed at Offset, nnn |
System RAM
failed. |
Replace the memory
modules.
|
System
Timer Error |
DMA, timers,
etc. |
Replace the system
board.
|
UMB
Upper Limit Segment Address, nnn |
Displays
the address of nnn of the upper limit of Upper Memory Blocks, indicating
releases segments of the BIOS. |
Status Message: no action required.
|
Video
BIOS Shadowed |
Video BIOS
successfully copied to shadow RAM. |
Status Message: no action required.
|
Return
to top
|