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Chapter 4 45
33 Initializes the silent boot module. Set the window for displaying text information.
37 Displaying sign-on message, CPU information, setup key message, and any OEM specific
information.
38 Initializes different devices through DIM. See DIM Code Checkpoints section of document
for more information. USB controllers are initialized at this point.
39 Initializes DMAC-1 & DMAC-2.
3A Initialize RTC date/time.
3B Test for total memory installed in the system. Also, Check for DEL or ESC keys to limit
memory test. Display total memory in the system.
3C Mid POST initialization of chipset registers.
40 Detect different devices (Parallel ports, serial ports, and coprocessor in CPU, ?? etc.)
successfully installed in the system and update the BDA, EBDA??etc.
50 Programming the memory hole or any kind of implementation that needs an adjustment in
system RAM size if needed.
52 Updates CMOS memory size from memory found in memory test. Allocates memory for
Extended BIOS Data Area from base memory.
60 Initializes NUM-LOCK status and programs the KBD typematic rate.
75 Initialize Int-13 and prepare for IPL detection.
78 Initializes IPL devices controlled by BIOS and option ROMs.
7A Initializes remaining option ROMs.
7C Generate and write contents of ESCD in NVRam.
84 Log errors encountered during POST.
85 Display errors to the user and gets the user response for error.
87 Execute BIOS setup if needed / requested. Check boot password if installed.
8C Late POST initialization of chipset registers.
8D Build ACPI tables (if ACPI is supported)
8E Program the peripheral parameters. Enable/Disable NMI as selected
90 Late POST initialization of system management interrupt.
A0 Check boot password if installed.
A1 Clean-up work needed before booting to OS.
A2 Takes care of runtime image preparation for different BIOS modules. Fill the free area in
F000h segment with 0FFh. Initializes the Microsoft IRQ Routing Table. Prepares the
runtime language module. Disables the system configuration display if needed.
A4 Initialize runtime language module. Display boot option popup menu.
A7 Displays the system configuration screen if enabled. Initialize the CPU??s before boot,
which includes the programming of the MTRR??s.
A8 Prepare CPU for OS boot including final MTRR values.
A9 Wait for user input at config display if needed.
Checkpoint Description