Intel® 64 Architecture x2APIC Specification
Introduction
The xAPIC architecture provided a key mechanism for
interrupt delivery in many generations of Intel processors and platforms across different market segments. This document
describes the x2APIC architecture which is extended from the xAPIC architecture (the latter was first implemented on Intel®
Pentium® 4 Processors, and extended the APIC architecture implemented on Pentium and P6 processors). Extensions to the
xAPIC architecture are intended primarily to increase processor addressability. The x2APIC architecture provides backward
compatibility to the xAPIC architecture and forward extendibility for future Intel platform innovations. Specifically,
x2APIC
• Retains all key elements of compatibility to the xAPIC architecture:
• delivery modes,
• interrupt and
processor priorities,
• interrupt sources,
• interrupt destination types;
• Provides extensions to scale processor
addressability for both the logical and physical destination modes;
• Adds new features to enhance performance of
interrupt delivery;
• Reduces complexity of logical destination mode interrupt delivery on link based
architectures.
Impacted Platform Components
x2APIC is architected to extend from the xAPIC architecture while
minimizing the impact on platform components. Specifically, support for the x2APIC architecture can be implemented in the
local APIC unit. All existing PCI/MSI capable devices and IOxAPIC unit should work with the x2APIC extensions defined in
this document. The x2APIC architecture also provides flexibility to cope with the underlying fabrics that connect the PCI
devices, IOxAPICs and Local APIC units. Modifications to ACPI interfaces to support x2APIC are described in the ACPI 4.0
specification.
Read the full Intel® 64 Architecture x2APIC Specification.
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Intel® 64 Architecture x2APIC Specification
Introduction
The xAPIC architecture provided a key mechanism for
interrupt delivery in many generations of Intel processors and platforms across different market segments. This document
describes the x2APIC architecture which is extended from the xAPIC architecture (the latter was first implemented on Intel®
Pentium® 4 Processors, and extended the APIC architecture implemented on Pentium and P6 processors). Extensions to the
xAPIC architecture are intended primarily to increase processor addressability. The x2APIC architecture provides backward
compatibility to the xAPIC architecture and forward extendibility for future Intel platform innovations. Specifically,
x2APIC
• Retains all key elements of compatibility to the xAPIC architecture:
• delivery modes,
• interrupt and
processor priorities,
• interrupt sources,
• interrupt destination types;
• Provides extensions to scale processor
addressability for both the logical and physical destination modes;
• Adds new features to enhance performance of
interrupt delivery;
• Reduces complexity of logical destination mode interrupt delivery on link based
architectures.
Impacted Platform Components
x2APIC is architected to extend from the xAPIC architecture while
minimizing the impact on platform components. Specifically, support for the x2APIC architecture can be implemented in the
local APIC unit. All existing PCI/MSI capable devices and IOxAPIC unit should work with the x2APIC extensions defined in
this document. The x2APIC architecture also provides flexibility to cope with the underlying fabrics that connect the PCI
devices, IOxAPICs and Local APIC units. Modifications to ACPI interfaces to support x2APIC are described in the ACPI 4.0
specification.
Read the full Intel® 64 Architecture x2APIC Specification.
