IA-64 Systems and ACPI 2.0 64-bit Tables

Updated: January 16, 2003 | Reviewed: July 8, 2008

The Intel Itanium-based systems that run 64-bit versions of Microsoft Windows operating systems must support the ACPI 2.0 64-bit fixed tables. Windows XP and Windows Server 2003 do not support the 0.71 interim tables. The ACPI 2.0 fixed tables allow for 64-bit addressing without requiring namespace changes. This means that ACPI 1.0 namespaces will still be valid.

Note: The Windows Logo Program for hardware requires that Itanium-based systems support the ACPI 2.0 fixed tables.

The additions made in ACPI 2.0 to accommodate 64-bit systems were typically made to the end of the existing tables, allowing for ACPI 1.0b backward compatibility.

The following tables must be added or updated in Itanium-based systems to meet the requirements in the ACPI 2.0 specification:

• Root System Description Pointer (RSDP) Structure

• Fixed ACPI Description Table (FADT)

• Firmware ACPI Control Structure (FACS)

• Multiple APIC Description Table (MADT)

• Extended System Description Table (XSDT)

Note: Itanium-based systems must use the new Extensible Firmware Interface (EFI) GUID for the ACPI 2.0 RSDP Structure. The EFI GUID for the ACPI 2.0 RSDP Structure pointer is: 8868E871-E4F1-11d3-BC22-0080C73C8881.
See ACPI 2.0 Specification section 5.2.4.2. This specification is available on the
ACPI web site .

The RSDP Structure must be implemented as defined in the ACPI 2.0 Specification, section 5.2.4.3. The Length, XsdtAddress, Extended Checksum, and Reserved fields were added in ACPI 2.0. The XsdtAddress field is 8 bytes, and provides the 64-bit address of the Extended Root System Description Table (XSDT). The Revision field must be set to 2.

The FADT has been extended in the ACPI 2.0 Specification; see section 5.2.8. Most of the reserved fields are now used: there are new fields for reset support, and new fields to provide extended addressing support using the Generic Addressing Structure (GAS) format.

The X_Firmware_Waking_Vector field added to the FACS. The X_Firmware_Waking_Vector is the 64-bit physical address of the Firmware Waking Vector and is reported using the GAS. See ACPI 2.0 Specification section 5.2.9.

The MADT defined in ACPI 2.0 Specification section 5.2.10.4 adds new APIC structure entries. The new entries include Local APIC Address Override Structure, I/O SAPIC, Local SAPIC, and Platform Interrupt Sources.

The XSDT was added in ACPI 2.0 Specification section 5.2.7. The XSDT provides identical functionality as the RSDT but accommodates physical addresses of DESCRIPTION HEADERs that are larger than 32 bits.

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