Technical information

53 Chapter 4
AMIBIOS POST Checkpoint Codes
When AMIBIOS performs the Power On Self Test, it writes diagnostic codes 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.
Uncompressed Initialization Codes
The uncompressed initialization checkpoint codes are listed in order of execution:
Bootblock Recovery Codes
The bootblock recovery 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 the 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.
Checkpoint Code Description
E0h The onboard floppy controller if available is initialized. Next, beginning the base
512KB memory
test.
E1h Initializing the interrupt vector table next.
E2h Initializing the DMA and Interrupt controllers next.
E6h Enabling the floppy drive controller and Timer IRQs.
Enabling internal cache memory.
Edh Initializing the floppy drive.
Eeh Looking for a floppy diskette in drive A:. Reading the
first sector of the diskette.
Efh A read error occurred while reading the floppy drive in drive A:.
F0h Next, searching for the AMIBOOT.ROM file in the root directory.