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BIOS Setup Information
Uncompressed Initialization Codes
The uncompressed initialization checkpoint hex codes are listed below in order of
execution:
Code Description
D0
NMI is disabled. CPU ID saved. INIT code checksum
verification will be started.
D1
Initializing the DMA controller, performing the keyboard
controller BAT test, starting memory refresh, and going to
4GB flat mode.
D3
To start memory sizing.
D4
Returning to real mode. Executing any OEM patches and
setting the stack.
D5
Passing control to the uncompressed code in shadow RAM
at E000:0000h.
The INIT code is copied to segment 0 and control will be
transferred to segment 0.
D6
Control is in segment 0. Next, checking if [Ctrl + Home]
was pressed and verifying the system BIOS checksum.
If [Ctrl + Home] was pressed or the system BIOS checksum
is bad, will go to checkpoint code E0h. Otherwise, going to
checkpoint code D7h.
D7
To pass control to interface module.
D8
Main BIOS runtime code is to be decompressed.
D9
Passing control to the main system BIOS in shadow RAM.