43
English
Checkpoint
Description
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 de-
tection of KB/MS using AMI KB-5.
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.
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POST Code Checkpoins
The POST code checkpoints are the largest set of checkpoints during the BIOS pre-boot
process. The following table describes the type of checkpoints that may occur during the
POST portion of the BIOS:
