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System Resources
4-2
AMI POST Code
Bootblock Initialization Code Checkpoints
The Bootblock initialization code sets up the chipset, memory and other
components before system memory is available. The following table de-
scribes the type of checkpoints that may occur during the bootblock initial-
ization portion of the BIOS:
Checkpoint
Description
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
fl
at mode with 4GB limit and GA20 enabled. Verify the bootblock
checksum.
D2
Disable CACHE before memory detection. Execute full memory sizing
module. Verify that
fl
at 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
fl
at mode is enabled.
D4
Test base 512KB memory. Adjust policies and cache
fi
rst 8MB. Set
stack.
D5
Bootblock code is copied from ROM to lower system memory and con-
trol is given to it. BIOS now executes out of RAM.
D6
Both key sequence and OEM speci
fi
c method is checked to determine
if BIOS recovery is forced. Main BIOS checksum is tested. If BIOS
recovery is necessary, control
fl
ows to checkpoint E0. See Bootblock
Recovery Code Checkpoints section of document for more informa-
tion.
D7
Restore CPUID value back into register. The Bootblock-Runtime in-
terface module is moved to system memory and control is given to it.
Determine whether to execute serial
fl
ash.
D8
The Runtime module is uncompressed into memory. CPUID informa-
tion 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 docu-
ment for more information.
