Filter
Top Products
Appendix D: Industrial Devices
57
POST Checkpoint Codes
When AMIBIOS performs the Power On Self Test, it writes diagnostic
codes checkpoint codes to I/O port 0080h where the POST code display
is connected.
Table D-4 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 checksum will be verified.
D1h
Initializing the DMA controller, performing the
keyboard controller BAT test, starting memory refresh,
and entering 4 GB flat 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.
D6h
Control is in segment 0. Next, checking if <Ctrl>
<Home> was pressed and verifying the system BIOS
checksum.
If either <Ctrl> <Home> was pressed or the system
BIOS checksum is bad, next will go to checkpoint code
E0h.
Otherwise, going to checkpoint code D7h.
D7h
Main BIOS runtime code is to be decompressed and
control to be passed to main BIOS in shadow RAM.