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54 Chapter 4
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. Programming the
memory hole or any kind of implementation that needs an adjustment in system
RAM size if needed.
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.
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.
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.
A9 Wait for user input at config display if needed.
AA Uninstall POST INT1Ch vector and INT09h vector. Deinitializes the ADM module.
AB Prepare BBS for Int 19 boot.
AC End of POST initialization of chipset registers.
B1 Save system context for ACPI.
00 Passes control to OS Loader (typically INT19h).
Checkpoint Description