Instruction Set Changes
Introduction
The Fast System Call/Return instruction pair was added in the Pentium® II processor:
SYSENTER— Fast System Call.
SYSEXIT— Fast Return from System Call.
A detailed description can be found in “Fast System Call/Return Instruction Pair” on page 708.
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).
Fast System Call/Return Instruction Pair
Background
Normally, when an application program (i.e., a program that is executing ...
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