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3 Getting Started
26
BIOS POST Checkpoint Codes
Bootblock Initialization Codes
The Bootblock initialization code sets up the chipset, memory
and other components before system memory is available. The
following table describes the type of checkpoints that may
occur during the bootblock initialization
.
Checkpoint Code Description
Before D1 Early chipset initialization is done. Early super I/O
initialization is done including RTC and keyboard
controller.
NMI is enabled.
D1 Perform keyboard controller BAT test. Checks if
waking up from power management suspend state.
Save power-on CPUID value in scratch CMOS.
D0 Go to flat mode with 4 GB 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 512 KB memory. Adjust policies and cache
first 8 MB. 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 Recov-
ery Code Checkpoints for more information.
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