Intel IA-32 Manuale Utente

9-56 Vol. 3A

In order to assure that the BIOS function is present, the caller must verify the carry flag, the
return code, and the 64-bit signature. The update count reflects the number of 2048-byte blocks
available for storage within one non-volatile RAM.

The loader version number refers to the revision of the update loader program that is included
in the system BIOS image.

This function integrates a new microcode update into the BIOS storage device. Table 9-14 lists
the parameters and return codes for the function.

AX

Function Code

0D042H

BL

Sub-function

01H - Write update

ES:DI 

Update Address

Real Mode pointer to the Intel Update structure. This buffer is 
2048 bytes in length if the processor supports only fixed-size 
microcode update or...

Real Mode pointer to the Intel Update structure. This buffer is 
64 KBytes in length if the processor supports a variable-size 
microcode update.

CX

Scratch Pad1

Real mode segment address of 64 KBytes of RAM block

DX

Scratch Pad2

Real mode segment address of 64 KBytes of RAM block

SI

Scratch Pad3

Real mode segment address of 64 KBytes of RAM block

SS:SP

Stack pointer

32 KBytes of stack minimum

CF

Carry Flag

Carry Set - Failure - AH Contains status
Carry Clear - All return values valid

AH

Return Code

Status of the call

AL

OEM Error

Additional OEM information

Return Codes (see Table 9-18 for code definitions

SUCCESS

The function completed successfully.

NOT_IMPLEMENTED

The function is not implemented. 

WRITE_FAILURE

A failure occurred because of the inability to write the storage 
device.

ERASE_FAILURE

A failure occurred because of the inability to erase the storage 
device.

READ_FAILURE

A failure occurred because of the inability to read the storage 
device.