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POST checkpoint codes
When AMIBIOS performs the POST routine, it writes diagnostic codes, that is
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. The following AMIBIOS POST checkpoint codes are valid for all
AMIBIOS products with a core BIOS date of 7/15/95 (Enhanced). These
options allow detailed analysis of a board that fails to operate correctly.
Uncompressed initialization codes
The uncompressed initialization checkpoint codes available are listed in order
of execution in Table 6-5.
Table 6-5. Uncompressed initialized codes
Checkpoint
code
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
Passing control to the interface module next.
D8h
The main system BIOS runtime code will be decompressed next.
D9h
Passing control to the main system BIOS in shadow RAM next.
POST checkpoint codes
Description
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