Intel SL22T Specifications download pdf (Page 3)

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INTRODUCTION

CHAPTER 1

INTRODUCTION

1.1 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 archi-

tecture (the latter was first implemented on Intel® Pentium® 4 Processors, and

extended the APIC architecture implemented on Pentium and P6 processors). Exten-

sions to the xAPIC architecture are intended primarily to increase processor addres-

sability. The x2APIC architecture provides backward compatibility to the xAPIC

architecture and forward extendability for future Intel platform innovations. Specifi-

cally, 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.

1.2 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.

The extensions provided in this specification translate into modifications to:

• the local APIC unit,

• the underlying fabrics connecting Message Signaled Interrupts (MSI) capable PCI

devices to local xAPICs,

• the underlying fabrics connecting the IOxAPICs to the local APIC units.

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Intel SL22T Specifications Page 3