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BIOS POST Checkpoint Codes
The following table describes the checkpoints and associated
beep codes, if any, that may occur during the POST portion of
the BIOS
.
Checkpoint
Code
Beep Code Description
01h One short
beep before
boot
02h Verify Real Mode. If the CPU is in protected
mode, turn on A20 and pulse the reset line,
forcing a shutdown 0.
NOTE: Hook routine should not alter DX,
which holds the powerup CPUID.
03h Disabel Non-Maskable Interrupts (NMI).
04h Get CPU type from CPU registers and other
methods.
Save CPU type in NVRAM.
NOTE: Hook routine should not alter DX,
which holds the powerup CPUID.
06h Initialize system hardware. Reset the DMA
controllers, disable video, clear any pending
interrupts from the real-time clock and
setup port B register.
07h Disable system ROM shadow and start to
execute ROMEXEC code from the flash part.
This task is pulled into the build only when
the ROMEXEC relocation is installed.
08h Initialize chipset registers to the Initial POST
Values.