Maintenance and Troubleshooting 4-5
TROUBLESHOOTING
This subsection provides information that helps isolate and repair computer malfunctions at
the field level. Step-by-step instructions on diagnosing and solving computer hardware
problems are provided.
If disassembly is required, see Sections 5 and 6. Connector pin assignments are explained in
the Appendix A. Jumper settings are explained in Section 2.
Error Messages
Messages may appear when booting the system unit. Table Section 4-2 describes the possi-
ble error messages and their meanings.
Table Section 4-2 System Error Messages
Message Description
8042 Gate – A20 error Gate A20 on the keyboard controller (8042) is not working.
Replace the 8042.
Address Line Short Error in the address decoding circuitry on the system board.
C: Drive Error Hard disk drive C: does not respond. Run the Setup to correct
this problem. Also, check the C: hard disk drive type in Setup
to make sure the hard disk drive type is correct.
C: Drive Failure Hard disk drive C: does not respond. Replace the hard disk
drive.
Cache Memory Bad, Do Not
Enable Cache
Cache memory is defective.
CH-2 Timer Error Most AT systems include two timers. There is an error in
Timer 2.
CMOS Battery State Low CMOS RAM is powered by a battery. The battery power is low.
Replace the RTC on the system board.
CMOS Checksum Failure After CMOS RAM values are saved, a checksum value is
generated for error checking. The previous value is different
from the current value. Run Setup.
CMOS System Options Not
Set
The values stored in CMOS RAM does not match the type
detected by the BIOS. Run Setup.
CMOS Display Type Mismatch The graphics type in CMOS RAM does not match the type
detected by the BIOS. Run Setup.
CMOS Memory Size Mismatch The amount of memory on the system board is different than
the amount in CMOS RAM. Run Setup.
CMOS time and date not set Run Setup to set the date and time in CMOS RAM.
D: Drive Error Hard disk drive D: does not respond. Run the Setup to correct
this problem. Also, check the D: hard disk drive type in Setup
to make sure the hard disk drive type is correct.
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