Before D1 - Early chipset initialization is done. Early super I/O initialization is done including RTC and keyboard controller. NMI is disabled.
D1 - Perform keyboard controller BAT test. Check if waking up from power management suspend state. Save power-on CPUID value in scratch CMOS.
D0 - Go to flat mode with 4GB limit and GA20 enabled. Verify the bootblock checksum.
D2 - Disable CACHE before memory detection. Execute full memory sizing module. Verify that flat mode is enabled.
D3 - If memory sizing module not executed, start memory refresh and do memory sizing in Bootblock code. Do additional chipset initialization. Re-enable CACHE. Verify that flat mode is enabled.
D4 - Test base 512KB memory. Adjust policies and cache first 8MB. Set stack.
D5 - Bootblock code is copied from ROM to lower system memory and control is given to it. BIOS now executes out of RAM.
D6 - Both key sequence and OEM specific method is checked to determine if BIOS recovery is forced. Main BIOS checksum is tested. If BIOS recovery is necessary, control flows to checkpoint E0. See Bootblock Recovery Code Checkpoints section of document for more information.
D7 - Restore CPUID value back into register. The Bootblock-Runtime interface module is moved to system memory and control is given to it. Determine whether to execute serial flash.
D8 - The Runtime module is uncompressed into memory. CPUID information is stored in memory.
D9 - Store the Uncompressed pointer for future use in PMM. Copying Main BIOS into memory. Leaves all RAM below 1MB Read-Write including E000 and F000 shadow areas but closing SMRAM.
DA - Restore CPUID value back into register. Give control to BIOS POST (ExecutePOSTKernel). See POST Code Checkpoints section of document for more information.
E0 - Initialize the floppy controller in the super I/O. Some interrupt vectors are initialized. DMA controller is initialized. 8259 interrupt controller is initialized. L1 cache is enabled.
E9 - Set up floppy controller and data. Attempt to read from floppy.
EA - Enable ATAPI hardware. Attempt to read from ARMD and ATAPI CDROM.
EB - Disable ATAPI hardware. Jump back to checkpoint E9.
EF - Read error occurred on media. Jump back to checkpoint EB.
E9 or EA - Determine information about root directory of recovery media.
F0 - Search for pre-defined recovery file name in root directory.
F1 - Recovery file not found.
F2 - Start reading FAT table and analyze FAT to find the clusters occupied by the recovery file.
F3 - Start reading the recovery file cluster by cluster.
F5 - Disable L1 cache.
FA - Check the validity of the recovery file configuration to the current configuration of the flash part.
FB - Make flash write enabled through chipset and OEM specific method. Detect proper flash part. Verify that the found flash part size equals the recovery file size.
F4 - The recovery file size does not equal the found flash part size.
FC - Erase the flash part.
FD - Program the flash part.
FF - The flash has been updated successfully. Make flash write disabled. Disable ATAPI hardware. Restore CPUID value back into register. Give control to F000 ROM at F000:FFF0h.
03 - Disable NMI, Parity, video for EGA, and DMA controllers. Initialize BIOS, POST, Runtime data area. Also initialize BIOS modules on POST entry and GPNV area. Initialized CMOS as mentioned in the Kernel Variable "wCMOSFlags."
04 - Check CMOS diagnostic byte to determine if battery power is OK and CMOS checksum is OK. Verify CMOS checksum manually by reading storage area. If the CMOS checksum is bad, update CMOS with power-on default values and clear passwords. Initialize status register A. Initializes data variables that are based on CMOS setup questions. Initializes both the 8259 compatible PICs in the system
05 - Initializes the interrupt controlling hardware (generally PIC) and interrupt vector table.
06 - Do R/W test to CH-2 count reg. Initialize CH-0 as system timer. Install the POSTINT1Ch handler. Enable IRQ-0 in PIC for system timer interrupt. Traps INT1Ch vector to "POSTINT1ChHandlerBlock."
08 - Initializes the CPU. The BAT test is being done on KBC. Program the keyboard controller command byte is being done after Auto detection of KB/MS using AMI KB-5.
C0 - Early CPU Init Start -- Disable Cache - Init Local APIC
C1 - Set up boot strap proccessor Information
C2 - Set up boot strap proccessor for POST
C5 - Enumerate and set up application proccessors
C6 - Re-enable cache for boot strap proccessor
C7 - Early CPU Init Exit
0A - Initializes the 8042 compatible Key Board Controller.
0B - Detects the presence of PS/2 mouse.
0C - Detects the presence of Keyboard in KBC port.
0E - Testing and initialization of different Input Devices. Also, update the Kernel Variables. Traps the INT09h vector, so that the POST INT09h handler gets control for IRQ1. Uncompress all available language, BIOS logo, and Silent logo modules.
13 - Early POST initialization of chipset registers.
24 - Uncompress and initialize any platform specific BIOS modules.
30 - Initialize System Management Interrupt.
2A - Initializes different devices through DIM. See DIM Code Checkpoints section of document for more information.
2C - Initializes different devices. Detects and initializes the video adapter installed in the system that have optional ROMs.
2E - Initializes all the output devices.
31 - Allocate memory for ADM module and uncompress it. Give control to ADM module for initialization. Initialize language and font modules for ADM. Activate ADM module.
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.
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.
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.
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).
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.
38 - Initialize different buses and perform the following functions: Boot Input Device Initialization (function 3); IPL Device Initialization (function 4); General Device Initialization (function 5). Function 3 searches for and configures PCI input devices and detects if system has standard keyboard controller. Function 4 searches for and configures all PnP and PCI boot devices. Function 5 configures all onboard peripherals that are set to an automatic configuration and configures all remaining PnP and PCI devices.
While control is in the different functions, additional checkpoints are output to port 80h as a word value to identify the routines under execution. The low byte value indicates the main POST Code Checkpoint. The high byte is divided into two nibbles and contains two fields. The details of the high byte of these checkpoints are as follows:
HIGH BYTE XY
The upper nibble 'X' indicates the function number that is being executed. 'X' can be from 0 to 7.
0 = func#0, disable all devices on the BUS concerned.
1 = func#1, static devices initialization on the BUS concerned.
2 = func#2, output device initialization on the BUS concerned.
3 = func#3, input device initialization on the BUS concerned.
4 = func#4, IPL device initialization on the BUS concerned.
5 = func#5, general device initialization on the BUS concerned.
6 = func#6, error reporting for the BUS concerned.
7 = func#7, add-on ROM initialization for all BUSes.
8 = func#8, BBS ROM initialization for all BUSes.
The lower nibble 'Y' indicates the BUS on which the different routines are being executed. 'Y' can be from 0 to 5.
0 = Generic DIM (Device Initialization Manager).
1 = On-board System devices.
2 = ISA devices.
3 = EISA devices.
4 = ISA PnP devices.
5 = PCI devices.
AC - First ASL check point. Indicates the system is running in ACPI mode.
AA - System is running in APIC mode.
01, 02, 03, 04, 05 - Entering sleep state S1, S2, S3, S4, or S5.
10, 20, 30, 40, 50 - Waking from sleep state S1, S2, S3, S4, or S5
