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BIOS Setup Information
Uncompressed Initialization Codes
The uncompressed initialization checkpoint hex codes are listed in order of execution:
Table 4-10.Uncompressed Initialization Codes
Code
Description
D0
NMI is disabled. CPU ID saved. INIT code check sum 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
Beginning memory sizing.
D4
Returning to real mode. Executing any OEM patches and setting the stack
next.
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 that [Ctr+Home] was pressed and
verifying the system BIOS check sum.
If either [Ctrl+Home] was pressed or the system BIOS checksum is bad,
go to checkpoint code E0h.
Otherwise, go to checkpoint code D7h.
D7
Passing control to interface module.
D8
Main BIOS runtime code is to be decompressed.
D9
Passing control to the main system BIOS in shadow RAM.