ADLINK Express-LPC - Manual (Page 74)

Express-LPC User’s Manual Page 74
9.1 Bootblock Initialization Code Checkpoints
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 portion of the BIOS:
Checkpoints may differ between different platforms based on system configuration.
Checkpoints may change due to vendor requirements, system chipset or option ROMs
from add-in PCI devices.
Checkpoint Description
Before D0 If boot block debugger is enabled, CPU cache-as-RAM functionality is enabled at this point.
Stack will be enabled from this point.
D0 Early Boot Strap Processor (BSP) initialization like microcode update, frequency and other CPU
critical initialization. Early chipset initialization is done.
D1 Early super I/O initialization is done including RTC and keyboard controller. Serial port is
enabled at this point if needed for debugging. NMI is disabled. Perform keyboard controller BAT
test. Save power-on CPUID value in scratch CMOS. Go to flat mode with 4GB limit and GA20
enabled.
D2 Verify the boot block checksum. System will hang here if checksum is bad.
D3 Disable CACHE before memory detection. Execute full memory sizing module. If memory sizing
module not executed, start memory refresh and do memory sizing in Boot block 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. Copies compressed boot block code to memory in right segments.
Copies BIOS from ROM to RAM for faster access. Performs main BIOS checksum and updates
recovery status accordingly.
D6 Both key sequence and OEM specific method is checked to determine if BIOS recovery is
forced. 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.
DC System is waking from ACPI S3 state
E1-E8, EC-EE OEM memory detection/configuration error. This range is reserved for chipset vendors & system
manufacturers. The error associated with this value may be different from one platform to the
next.