Advanced Configuration and Power Interface Specification

Advanced Configuration and Power Interface Specification
Field
Byte
Length
Byte
Offset
Description
Access Size 1 3 Specifies access size.
0 Undefined (legacy reasons)
1 Byte access
2 Word access
3 Dword access
4 QWord access
Address 8 4 The 64-bit address of the data structure or register in the given
address space (relative to the processor). (See below for specific
formats.)
Table 5-27 Address Space Format
Address Space
0–System Memory
1–System I/O
2–PCI Configuration
Space
0x7F–Functional
Fixed Hardware
Format
The 64-bit physical memory address (relative to the processor) of the register. 32-bit
platforms must have the high DWORD set to 0.
The 64-bit I/O address (relative to the processor) of the register. 32-bit platforms
must have the high DWORD set to 0.
PCI Configuration space addresses must be confined to devices on
PCI Segment Group 0, bus 0. This restriction exists to accommodate access to fixed
hardware prior to PCI bus enumeration. The format of addresses are defined as
follows:
WORD Location
Description
Highest WORD Reserved (must be 0)
… PCI Device number on bus 0
…
PCI Function number
Lowest WORD
Offset in the configuration space header
For example: Offset 23h of Function 2 on device 7 on bus 0 segment 0 would be
represented as: 0x0000000700020023.
Use of GAS fields other than Address_Space_ID is specified by the CPU
manufacturer. The use of functional fixed hardware carries with it a reliance on OS
specific software that must be considered. OEMs should consult OS vendors to
ensure that specific functional fixed hardware interfaces are supported by specific
operating systems.
5.2.4 Universal Uniform Identifiers (UUID)
UUIDs (Universally Unique IDentifiers), also known as GUIDs (Globally Unique IDentifiers) are
128 bit long values that extremely likely to be different from all other UUIDs generated until 3400
A.D. UUIDs are used to distinguish between callers of ASL methods, such as _DSM and _OSC.
The format of both the binary and string representations of UUIDs along with an algorithm to
generate them is specified in ISO/IEC 11578:1996 and can be found as part of the Distributed
Computing Environment 1.1: Remote Procedure Call specification, which can be found in “Links to
108 April, 2015 Version 6.0