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 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.

 

 

B-1

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SUPER MICRO Computer H8QG6+-F, H8QGI+-F user manual Appendix B Bios Post Checkpoint Codes, Uncompressed Initialization Codes