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