B-1
Appendix B: BIOS POST Checkpoint Codes
Appendix B
BIOS POST Checkpoint Codes
When AMIBIOS performs the Power On Self Test, it writes checkpoint codes to I/O
port 0080h. If the computer cannot complete the boot process, diagnostic equipment
can be attached to the computer to read I/O port 0080h.
B-1 Uncompressed
Initialization
Codes
The uncompressed initialization checkpoint codes are listed in order of execution:
Checkpoint Code Description
D0h
The NMI is disabled. Power on delay is starting. Next, the initialization code check-
sum will be verifi ed.
D1h
Initializing the DMA controller, performing the keyboard controller BAT test, starting
memory refresh and entering 4 GB fl at mode next.
D3h
Starting memory sizing next.
D4h
Returning to real mode. Executing any OEM patches and setting the Stack next.
D5h
Passing control to the uncompressed code in shadow RAM at E000:0000h. The
initialization code is copied to segment 0 and control will be transferred to segment
0.
Summary of Contents for AS 4040C-TR
Page 1: ...AS 4040C TR AS 4040C 8R USER S MANUAL 1 0 ...
Page 5: ...v Preface Notes ...
Page 10: ...x Notes AS4040C TR 4040C 8R User s Manual ...
Page 16: ...1 6 AS4040C TR 4040C 8R User s Manual Notes ...
Page 62: ...5 28 AS4040C TR 4040C 8R User s Manual Figure 5 6 Driver Installation Screen Shot ...
Page 72: ...6 10 AS4040C TR 4040C 8R User s Manual Figure 6 8 Removing a Power Supply Module ...
Page 92: ...A 2 AS4040C TR 4040C 8R User s Manual Notes ...
Page 100: ...B 8 AS4040C TR 4040C 8R User s Manual Notes ...
Page 104: ...C 4 AS4040C TR 4040C 8R User s Manual Notes ...