Intel Motherboard Raptor AT Installation Manual page 67

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
The NMI is disabled. Power on delay is starting. Next,
D0h
the initialization code checksum will be verified.
Initializing the DMA controller, performing the
D1h keyboard controller BAT test, starting memory refresh,
and entering 4 GB flat mode next.
D3h Starting memory sizing next.
Returning to real mode. Executing any OEM patches
D4h
and setting the stack next.
Passing control to the uncompressed code in shadow
D5h RAM at E000:0000h.The initialization code is copied to
segment 0 and control will be transferred to segment 0.
Control is in segment 0. Next, checking if <Ctrl>
<Home> was pressed and verifying the system BIOS
checksum.
D6h 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.
Main BIOS runtime code is to be decompressed and
D7h
control to be passed to main BIOS in shadow RAM.
Appendix D: Industrial Devices
Description
57