6-8 Troubleshooting and Repair
Beep
Code
Diagnostic
Code
Description
Test Performed
3-2-4
27h
Keyboard controller test in
progress or failure.
The self-test command (AAh) is issued to the
8042 (keyboard controller) and the results are
monitored. Failure results in a system halt.
None
28h
CMOS RAM power failure
and checksum calculation
test in progress.
The power-fail bit in CMOS RAM is tested and
the lower CMOS RAM area is being
checksummed. A failure does not result in
system halt.
None
29h
CMOS RAM configuration
validation for video in
progress.
No specific test is performed - just indicates
that the configuration specified in CMOS for
video is being matched against the actual
installation. A failure does not result in a system
halt.
3-3-4
2Bh
Screen memory test in
progress or failure.
The video buffers (B0000h and B8000h) are
tested with a pattern test and a rolling ones
test. Failure will result in a beep code but not a
system halt.
3-4-1
2Ch
Screen initialization in
progress.
Until the video installation is confirmed, any
calls to INT 10h Function 0 (set mode) will be
prefaced with the diagnostic code. There is no
expected failure from this.
3-4-2
2Dh
Screen retrace test in
progress or failure.
Over a period of time, the retrace bit (bit0) in
the appropriate CRT controller status register
(either port 3BAh or 3DAh) is read and tested.
The retrace bit should toggle from 0 to 1, then 1
to 0 within the time period.
None
2Eh
Search for video ROM in
progress.
No specific test is performed by the system
BIOS - just indicates that the BIOS is about to
jump to the initialization code in the video
option ROM.
none
30h
Screen running with video
ROM.
No specific test is performed - just indicates
that a video option ROM was found and
believed to be operating.
none
31h
Monochrome monitor
operable.
No specific test is performed - just indicates
that the BIOS believes a monochrome monitor
is installed and is operating.
none
32h
Colour monitor (40-column)
operable.
No specific test is performed - just indicates
that the BIOS believes a colour monitor is
installed and is operating. The mode has been
set to 40-column as selected by the user in
CMOS RAM.
none
33h
Colour monitor (80-column)
operable.
No specific test is performed - just indicates
that the BIOS believes a colour monitor is
installed and is operating. The mode has been
set to 80-column as selected by the user in
CMOS RAM.
4-2-1
34h
Timer-tick interrupt test in
progress or failure.
All interrupts expect the timer-tick interrupt are
masked off at the interrupt controllers. If a
timer-tick interrupt does not occur during a
specific time period, an error message is
displayed on the screen. The system does not
halt.
