4-16 Troubleshooting and Repair
Table Section 4-5 Diagnostic Output and Beep Codes
Code
Beeps
Description of Test or Failure at POST
4C
shadow video BIOS ROM
4E
display copyright notice
50
display CPU type and speed
52
test keyboard
54
set key click if enabled
56
enable keyboard
58
2-2-3-1
test for unexpected interrupts
5A
display prompt “F2 to run Setup”
5C
test RAM between 512 and 640k
60
test extended memory
62
test extended memory address lines
64
jump to UserPatch1
66
configure advanced cache registers
68
enable extended and CPU caches
6A
display external cache size
6C
display shadow message
6E
display non-disposable segments
70
display error messages
72
check for configuration errors
74
test real-time clock
76
check for keyboard errors
7C
set up hardware interrupt vectors
7E
test coprocessor if present
80
disable on-board I/O ports
82
detect and install external RS-232 ports
84
detect and install external parallel ports
86
reinitialize on-board I/O ports
88
initialize BIOS data area/password check
8A
initialize extended BIOS data area
8C
initialize diskette controller
90
initialize hard disk controller
91
initialize local-bus hard disk controller
92
jump to UserPatch2
94
disable A20 address line
96
clear huge ES segment register
98
search for option ROMs