Advanced Configuration and Power Interface Specification

Advanced Configuration and Power Interface Specification
Field
Byte
Length
Byte
Offset
Description
Length 4 4 Length, in bytes, of the entire table. The length implies the
number of Entry fields (n) at the end of the table.
Revision 1 8 1
Checksum 1 9 Entire table must sum to zero.
OEMID 6 10 OEM ID
OEM Table ID 8 16 For the XSDT, the table ID is the manufacture model ID. This
field must match the OEM Table ID in the FADT.
OEM Revision 4 24 OEM revision of XSDT table for supplied OEM Table ID.
Creator ID 4 28 Vendor ID of utility that created the table. For tables containing
Definition Blocks, this is the ID for the ASL Compiler.
Creator Revision 4 32 Revision of utility that created the table. For tables containing
Definition Blocks, this is the revision for the ASL Compiler.
Entry 8*n 36 An array of 64-bit physical addresses that point to other
DESCRIPTION_HEADERs. OSPM assumes at least the
DESCRIPTION_HEADER is addressable, and then can further
address the table based upon its Length field.
5.2.9 Fixed ACPI Description Table (FADT)
The Fixed ACPI Description Table (FADT) defines various fixed hardware ACPI information vital
to an ACPI-compatible OS, such as the base address for the following hardware registers blocks:
PM1a_EVT_BLK, PM1b_EVT_BLK, PM1a_CNT_BLK, PM1b_CNT_BLK, PM2_CNT_BLK,
PM_TMR_BLK, GPE0_BLK, and GPE1_BLK.
The FADT also has a pointer to the DSDT that contains the Differentiated Definition Block, which
in turn provides variable information to an ACPI-compatible OS concerning the base system design.
All fields in the FADT that provide hardware addresses provide processor-relative physical
addresses.
Note: If the HW_REDUCED_ACPI flag in the table is set, OSPM will ignore fields related to the ACPI
HW register interface: Fields at offsets 46 through 108 and 148 through 232, as well as FADT Flag
bits 1, 2, 3,7,8,12,13, 14, 16 and 17).
Table 5-34 Fixed ACPI Description Table (FADT) Format
Field
Byte
Length
Byte
Offset
Description
Header
Signature 4 0 ‘FACP’. Signature for the Fixed ACPI Description Table. (This
signature predates ACPI 1.0, explaining the mismatch with
this table's name.)
Length 4 4 Length, in bytes, of the entire FADT.
FADT Major Version 1 8 6
Major Version of this FADT structure, in "Major.Minor" form,
where 'Minor' is the value in the Minor Version Field (Byte
offset 131 in this table)
116 April, 2015 Version 6.0