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Uncompressed Initialization Codes
The uncompressed initialization codes are listed in order of execution.
SYSTEM
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 verifiying the system BIOS checksum. If <Ctrl> <Home>
was pressed or the system BIOS checksum is bad, next will go to
checkpoint code E0h. Otherwise, going to 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.
