Boot Block Recovery Code Checkpoints

Checkpoint	Description

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 the “Boot Block Recovery Code Checkpoints” section 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 1 MB 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 the “POST Code Checkpoints” section for more information.

The boot block recovery code gets control when the BIOS determines that a BIOS recovery is required because the user has forced the update or the BIOS checksum is corrupt. Refer to “BIOS Recovery” section on page 83 for more information. The following table describes the type of checkpoints that may occur during the boot block recovery portion of the BIOS.

Checkpoint	Description

E0	Initialize the floppy controller in the super I/O. Some interrupt vectors are initialized. DMA
	controller is initialized. 8259 interrupt controller is initialized. L1 cache is enabled.

E9	Set up floppy controller and data. Attempt to read from floppy.

EA	Enable ATAPI hardware. Attempt to read from ARMD and ATAPI CDROM.

EB	Disable ATAPI hardware. Jump back to checkpoint E9.

EF	Read error occurred on media. Jump back to checkpoint EB.

E9 or EA	Determine information about root directory of recovery media.

F0	Search for pre-defined recovery file name in root directory.

F1	Recovery file not found.

F2	Start reading FAT table and analyze FAT to find the clusters occupied by the recovery file.

F3	Start reading the recovery file cluster by cluster.

F5	Disable L1 cache.

FA	Check the validity of the recovery file configuration to the current configuration of the flash
	part.

FB	Make flash write enabled through chipset and OEM specific method. Detect proper flash
	part. Verify that the found flash part size equals the recovery file size.

F4	The recovery file size does not equal the found flash part size.

FC	Erase the flash part.

FD	Program the flash part.

Aspire Z3750 / Z3751 / Z5750 / Z5751 AIO Computer Service Guide