Firmware Interface Table

BIOS Specification

ID Date Version Classification
599500 03/01/2025 Public
Document Table of Contents
Document Table of Contents
Legal Revision History Firmware Interface Table Introduction Summary Of Key Requirements FIT Pointer Firmware Interface Table
Legal
Revision History
Firmware Interface Table Introduction
Summary Of Key Requirements
FIT Pointer
FIT Pointer FIT Pointer Rules
FIT Pointer Rules
Firmware Interface Table
Firmware Interface Table FIT Ordering Rules FIT Header (Type 0) Rules Microcode Update (Type 1) Rules Startup ACM (Type 2) Rules Diagnostic ACM (Type 3) Rules Platform Boot Policy (Type 4) Rules Memory Microcontroller Firmware Image (Type 5) Rules FIT Reset State (Type 6) Rules BIOS Startup Module (Type 7) Rules TPM Policy Record (Type 8) Rules BIOS Policy Data Record (Type 9) Rules Intel® TXT Policy Data Record (Type 0xA) Rules Key Manifest Record (Type 0xB) Rules Boot Policy Manifest (Type 0xC) Rules FSP Boot Manifest (Type 0xD) Rules Intel® CSE Secure Boot (Type 0x10) Rules Vendor Authorized Boot Provisioning Table (Type 0x1A) Rules Vendor Authorized Boot Key Manifest (Type 0x1B) Rules Vendor Authorized Boot Image Manifest (Type 0x1C) Rules Vendor Authorized Boot Image Descriptors (Type 0x1D) Rules (Deprecated) VAB Authorization Code Patch Image Manifest (Type 0x1E) Rules SACM Debug Record (Type 0x2C) Rules Feature Policy Record (Type 0x2D) Rules Granular SCRTM Error Record (Type 0x2E) Rules
FIT Ordering Rules
FIT Header (Type 0) Rules
Microcode Update (Type 1) Rules
Startup ACM (Type 2) Rules
Startup ACM (Type 2) Rules Legacy Record Modern Record CPU Processing Rules
Legacy Record
Modern Record
CPU Processing Rules
Diagnostic ACM (Type 3) Rules
Platform Boot Policy (Type 4) Rules
Memory Microcontroller Firmware Image (Type 5) Rules
FIT Reset State (Type 6) Rules
BIOS Startup Module (Type 7) Rules
TPM Policy Record (Type 8) Rules
TPM Policy Record (Type 8) Rules TPM Enabling Policy
TPM Enabling Policy
BIOS Policy Data Record (Type 9) Rules
Intel® TXT Policy Data Record (Type 0xA) Rules
Intel® TXT Policy Data Record (Type 0xA) Rules TXT Configuration Policy
TXT Configuration Policy
Key Manifest Record (Type 0xB) Rules
Boot Policy Manifest (Type 0xC) Rules
FSP Boot Manifest (Type 0xD) Rules
Intel® CSE Secure Boot (Type 0x10) Rules
Vendor Authorized Boot Provisioning Table (Type 0x1A) Rules
Vendor Authorized Boot Key Manifest (Type 0x1B) Rules
Vendor Authorized Boot Image Manifest (Type 0x1C) Rules
Vendor Authorized Boot Image Descriptors (Type 0x1D) Rules (Deprecated)
VAB Authorization Code Patch Image Manifest (Type 0x1E) Rules
SACM Debug Record (Type 0x2C) Rules
Feature Policy Record (Type 0x2D) Rules
Granular SCRTM Error Record (Type 0x2E) Rules

CPU Processing Rules

CPU will scan iteratively Type 2 records:

  1. Legacy CPU supporting only record version 0x100 will process it and will load ACM pointed by the address field.
  2. Modern CPU supporting only records version 0x200 will skip record version 0x100 and will continue scanning.
  3. CPU will read Extended Family, Extended Model, Type, Family and Model values from record version 0x200 and will construct full FMS_​Target value supported by this record. It will assume Stepping value equal 0.
  4. CPU will read Extended Family, Extended Model, Type, Family and Model Mask values from record version 0x200 and will construct full FMS_​Mask value supported by this record. It will assume SteppingMask value equal 0
  5. CPU will read own FMS value and apply the check:

IF (bitwise (FMS & FMS_​Mask) equals FMS_​Target)

it will load ACM pointed to by the address field.

ELSE

it will continue scanning.

Note:It might occur that one single ACM is designed to support two or more essentially different CPU microarchitectures such that creation of a Mask value is onerous or even impossible. In such a case BIOS shall create separate version 0x200 records each supporting one CPU microarchitecture but pointing to the same ACM.
Diagnostic ACM (Type 3) Rules