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48 Chapter 4
Device Initialization Manager code checkpoints
The Device Initialization Manager (DIM) module gets control at various times during BIOS POST to initialize
different BUSes. The following table describes the main checkpoints where the DIM module is accessed:
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.
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.
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.
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
2A Initialize different buses and perform the following functions: Reset, Detect, and
Disable (function 0); Static Device Initialization (function 1); Boot Output Device
Initialization (function 2). Function 0 disables all device nodes, PCI devices, and PnP
ISA cards. It also assigns PCI bus numbers. Function 1 initializes all static devices
that include manual configured onboard peripherals, memory and I/O decode
windows in PCI-PCI bridges, and noncompliant PCI devices. Static resources are
also reserved. Function 2 searches for and initializes any PnP, PCI, or AGP video
devices.
Checkpoint Description