Table 5-3 Root System Description Pointer Structure
Field
|
Byte Length
|
Byte Offset
|
Description
|
Signature
|
8
|
0
|
“RSD PTR ” (Notice that this signature must contain a trailing blank character.)
|
Checksum
|
1
|
8
|
This is the checksum of the fields defined in the ACPI 1.0 specification. This includes only the first 20 bytes of this table, bytes 0 to 19, including the checksum field. These bytes must sum to zero.
|
OEMID
|
6
|
9
|
An OEM-supplied string that identifies the OEM.
|
Revision
|
1
|
15
|
The revision of this structure. Larger revision numbers are backward compatible to lower revision numbers. The ACPI version 1.0 revision number of this table is zero. The current value for this field is 2.
|
RsdtAddress
|
4
|
16
|
32 bit physical address of the RSDT.
|
Length
|
4
|
20
|
The length of the table, in bytes, including the header, starting from offset 0. This field is used to record the size of the entire table.
|
XsdtAddress
|
8
|
24
|
64 bit physical address of the XSDT.
|
Extended Checksum
|
1
|
32
|
This is a checksum of the entire table, including both checksum fields.
|
Reserved
|
3
|
33
|
Reserved field
| -
All system description tables begin with the structure shown in Table 5-4. The Signature field determines the content of the system description table. System description table signatures defined by this specification are listed in Table 5-5.
Field
|
Byte Length
|
Byte Offset
|
Description
|
Signature
|
4
|
0
|
The ASCII string representation of the table identifier. Notice that if OSPM finds a signature in a table that is not listed in Table 5-5, OSPM ignores the entire table (it is not loaded into ACPI namespace); OSPM ignores the table even though the values in the Length and Checksum fields are correct.
|
Length
|
4
|
4
|
The length of the table, in bytes, including the header, starting from offset 0. This field is used to record the size of the entire table.
|
Revision
|
1
|
8
|
The revision of the structure corresponding to the signature field for this table. Larger revision numbers are backward compatible to lower revision numbers with the same signature.
|
Checksum
|
1
|
9
|
The entire table, including the checksum field, must add to zero to be considered valid.
|
OEMID
|
6
|
10
|
An OEM-supplied string that identifies the OEM.
|
OEM Table ID
|
8
|
16
|
An OEM-supplied string that the OEM uses to identify the particular data table. This field is particularly useful when defining a definition block to distinguish definition block functions. The OEM assigns each dissimilar table a new OEM Table ID.
|
OEM Revision
|
4
|
24
|
An OEM-supplied revision number. Larger numbers are assumed to be newer revisions.
|
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.
|
For OEMs, good design practices will ensure consistency when assigning OEMID and OEM Table ID fields in any table. The intent of these fields is to allow for a binary control system that support services can use. Because many support functions can be automated, it is useful when a tool can programmatically determine which table release is a compatible and more recent revision of a prior table on the same OEMID and OEM Table ID.
Tables 5-5 and 5-6 contain the system description table signatures defined by this specification. These system description tables may be defined by ACPI and documented within this specification (Table 5-5) or they may be simply reserved by ACPI and defined by other industry specifications (Table 5-6). This allows OS and platform specific tables to be defined and pointed to by the RSDT/XSDT as needed. For tables defined by other industry specifications, the ACPI specification acts as gatekeeper to avoid collisions in table signatures.
Table signatures will be reserved by the ACPI promoters and posted independently of this specification in ACPI errata and clarification documents on the ACPI web site. Requests to reserve a 4-byte alphanumeric table signature should be sent to the email address info@acpi.info and should include the purpose of the table and reference URL to a document that describes the table format. Tables defined outside of the ACPI specification may define data value encodings in either little endian or big endian format. For the purpose of clarity, external table definition documents should include the endian-ness of their data value encodings.
Since reference URLs can change over time and may not always be up-to-date in this specification, a separate document containing the latest known reference URLs can be found at: http://www.acpi.info/DOWNLOADS/referenceurls.pdf. If this document does not exist at this URL, then there are currently no updates available.
Signature
|
Description
|
Reference
|
“APIC”
|
Multiple APIC Description Table
|
Section 5.2.12, “Multiple APIC Description Table”
|
“BERT”
|
Boot Error Record Table
|
Section 17.3.1, “Boot Error Source”
|
“CPEP”
|
Corrected Platform Error Polling Table
|
Section 5.2.18, “Corrected Platform Error Polling Table”
|
“DSDT”
|
Differentiated System Description Table
|
Section 5.2.11.1, “Differentiated System Description Table”
|
“ECDT”
|
Embedded Controller Boot Resources Table
|
Section 5.2.15, “Embedded Controller Boot Resources Table”
|
“EINJ”
|
Error Injection Table
|
Section 17.5.1, “Error Injection Table”
|
“ERST”
|
Error Record Serialization Table
|
Section 17.4, “Error Serialization”
|
”FACP”
|
Fixed ACPI Description Table (FADT)
|
Section 5.2.9, “Fixed ACPI Description Table”
|
“FACS”
|
Firmware ACPI Control Structure
|
Section 5.2.10, “Firmware ACPI Control Structure”
|
“HEST”
|
Hardware Error Source Table
|
Section 17.3.2, “ACPI Error Source”
|
“MSCT”
|
Maximum System Characteristics Table
|
Section 5.2.19, “Maximum System Characteristics Table”
|
“OEMx”
|
OEM Specific Information Tables
|
OEM Specific tables. All table signatures starting with “OEM” are reserved for OEM use.
|
“PSDT”
|
Persistent System Description Table
|
Section 5.2.11.3, “Persistent System Description Table”
|
“RSDT”
|
Root System Description Table
|
Section 5.2.7, “Root System Description Table”
|
“SBST”
|
Smart Battery Specification Table
|
Section 5.2 14, “Smart Battery Table”
|
“SLIT”
|
System Locality Distance Information Table
|
Section 5.2.17, “System Locality Distance Information Table”
|
“SRAT”
|
System Resource Affinity Table
|
Section 5.2.16, “System Resource Affinity Table”
|
“SSDT”
|
Secondary System Description Table
|
Section 5.2.11.2, “Secondary System Description Table”
|
“XSDT”
|
Extended System Description Table
|
Section 5.2.8, “Extended System Description Table”
|
Signature
|
Description and External Reference
|
“BOOT”
|
Simple Boot Flag Table
See: Microsoft Simple Boot Flag Specification
http://www.microsoft.com/whdc/resources/respec/specs/simp_boot.mspx
|
“DBGP”
|
Debug Port Table
Microsoft Debug Port Specification
http://www.microsoft.com/HWDEV/PLATFORM/pcdesign/LR/debugspec.asp
|
“DMAR”
|
DMA Remapping Table
http://download.intel.com/technology/computing/vptech/Intel(r)_VT_for_Direct_IO.pdf
|
“ETDT”
|
Event Timer Description Table (Obsolete)
IA-PC Multimedia Timers Specification. This signature has been superseded by “HPET” and is now obsolete.
|
“HPET”
|
IA-PC High Precision Event Timer Table
IA-PC High Precision Event Timer Specification
http://www.intel.com/hardwaredesign/hpetspec_1.pdf
|
“IBFT”
|
iSCSI Boot Firmware Table
http://www.microsoft.com/whdc/system/platform/firmware/ibft.mspx
|
“IVRS”
|
I/O Virtualization Reporting Structure
http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/34434.pdf
|
“MCFG”
|
PCI Express memory mapped configuration space base address Description Table
PCI Firmware Specification, Revision 3.0
http://pcisig.com
|
“MCHI”
|
Management Controller Host Interface Table
DSP0256 Management Component Transport Protocol (MCTP) Host Interface Specification
http://www.dmtf.org/standards/published_documents/DSP0256_1.0.0a.pdf
|
“SPCR”
|
Serial Port Console Redirection Table
Microsoft Serial Port Console Redirection Table
http://www.microsoft.com/HWDEV/PLATFORM/server/headless/SPCR.asp
|
“SPMI”
|
Server Platform Management Interface Table
ftp://download.intel.com/design/servers/ipmi/IPMIv2_0rev1_0.pdf
|
“TCPA”
|
Trusted Computing Platform Alliance Capabilities Table
TCPA PC Specific Implementation Specification
https://www.trustedcomputinggroup.org/home
|
“UEFI”
|
UEFI ACPI Data Table
UEFI Specification
http://www.uefi.org
|
“WAET”
|
Windows ACPI Enlightenment Table
http://www.microsoft.com/whdc/system/platform/virtual/WAET.mspx
|
“WDAT”
|
Watch Dog Action Table
Requirements for Hardware Watchdog Timers Supported by Windows – Design Specification
http://www.microsoft.com/whdc/system/sysinternals/hw-wdt.mspx
|
“WDRT”
|
Watchdog Resource Table
Watchdog Timer Hardware Requirements for Windows Server 2003
http://www.microsoft.com/whdc/system/CEC/watchdog.mspx
| -
Root System Description Table (RSDT)
OSPM locates that Root System Description Table by following the pointer in the RSDP structure. The RSDT, shown in Table 5-7, starts with the signature ‘RSDT’ followed by an array of physical pointers to other system description tables that provide various information on other standards defined on the current system. OSPM examines each table for a known signature. Based on the signature, OSPM can then interpret the implementation-specific data within the table.
Platforms provide the RSDT to enable compatibility with ACPI 1.0 operating systems. The XSDT, described in the next section, supersedes RSDT functionality.
Table 5-7 Root System Description Table Fields (RSDT)
Field
|
Byte Length
|
Byte Offset
|
Description
|
Header
|
|
|
|
Signature
|
4
|
0
|
‘RSDT’ Signature for the Root System Description Table.
|
Length
|
4
|
4
|
Length, in bytes, of the entire RSDT. 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 RSDT, 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 RSDT 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
|
4*n
|
36
|
An array of 32-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.
| -
Extended System Description Table (XSDT)
The XSDT provides identical functionality to the RSDT but accommodates physical addresses of DESCRIPTION HEADERs that are larger than 32-bits. Notice that both the XSDT and the RSDT can be pointed to by the RSDP structure. An ACPI-compatible OS must use the XSDT if present.
Table 5-8 Extended System Description Table Fields (XSDT)
Field
|
Byte Length
|
Byte Offset
|
Description
|
Header
|
|
|
|
Signature
|
4
|
0
|
‘XSDT’. Signature for the Extended System Description Table.
|
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.
| -
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.
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