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The Unabridged Pentium 4 IA32 Processor Genealogy by Bob Colwell, Tom Shanley

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Instruction Set Changes

Introduction

The Fast System Call/Return instruction pair was added in the Pentium® II processor:

Support for the new instructions is indicated in the capability bit mask returned in the EDX register (bit 11) on executing a type 1 CPUID request (see Figure 28-1 on page 708).

Figure 28-1. CPUID Request Type 1 EDX Content

Fast System Call/Return Instruction Pair

Background

Normally, when an application program (i.e., a program that is executing ...

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