NEC VERSA 6000 Series Service Manual page 78

3-10 Troubleshooting and Repair
Beep Diagnostic
Code
Code
4-2-3 36h
4-2-4 37h
4-3-1 38h
4-3-2 3Ah
4-3-4 3Bh
4-4-1 3Ch
4-4-2 3Dh
Table 3-3 BIOS Beep Codes
Description
Gate A20 failure.
Unexpected interrupt in
protected mode.
RAM test of memory
above 64K in progress or
failure.
Programmable interval
timer channel 2 test in
progress or failure.
Real-time clock test in
progress or failure.
Serial port test in progress
or failure.
Parallel port test in
progress or failure.
Test Performed
To test extended memory, the
processor must be placed in protected
mode and the A20 line must be
enabled. For the memory tests, the
BIOS generally uses the keyboard
controller to enable A20. If the A20 line
is not properly set during the memory
test, an error message is displayed on
the screen and the memory test are
suspended. The system does not halt.
During the memory tests, the processor
is placed in protected mode. All
interrupts in the interrupt descriptor
table are initialized to point to special
handler that displays a message on the
screen. All hardware interrupt are
disabled. The system does not halt
when an unexpected interrupt occurs.
The memory above the first 64K is
tested with a rolling ones test and a
pattern test. All success and failure
messages are displayed on the screen
and POST will continue.
Over a period of time, the current count
values in timer 2 are read and
accumulated by ORing them into the
values read so far. It is expected that
during the time period, all bits will be
set. If an error is detected, an error
message will be displayed on the
screen and POST will continue.
Over a period of time, the Update-In-
Progress bit of Status Register A of
the real-time clock is read and tested.
The bit should toggle from 0 to 1 within
the time period.
Pattern test of one or more of the
installed serial ports. If a failure is
detected, an error message will be
displayed and POST will continue.
Rolling ones test is done to one of the
installed parallel ports. If a failure is
detected, an error message displays.