Intel ARCHITECTURE IA-32 User Manual Page 598

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17-6 Vol. 3A
IA-32 ARCHITECTURE COMPATIBILITY
Bit scan instructions.
Double-shift instructions.
Byte set on condition instruction.
Move with sign/zero extension.
Generalized multiply instruction.
MOV to and from control registers.
MOV to and from test registers (now obsolete).
MOV to and from debug registers.
RSM (resume from SMM). This instruction was introduced in the Intel386 SL and
Intel486 SL processors.
The following instructions were added in the Intel 387 math coprocessor:
FPREM1.
FUCOM, FUCOMP, and FUCOMPP.
17.13. OBSOLETE INSTRUCTIONS
The MOV to and from test registers instructions were removed from the Pentium processor and
future IA-32 processors. Execution of these instructions generates an invalid-opcode exception
(#UD).
17.14. UNDEFINED OPCODES
All new instructions defined for IA-32 processors use binary encodings that were reserved on
earlier-generation processors. Attempting to execute a reserved opcode always results in an
invalid-opcode (#UD) exception being generated. Consequently, programs that execute
correctly on earlier-generation processors cannot erroneously execute these instructions and
thereby produce unexpected results when executed on later IA-32 processors.
17.15. NEW FLAGS IN THE EFLAGS REGISTER
The section titled “EFLAGS Register” in Chapter 3, “Basic Execution Environment,” of the
IA-32 Intel® Architecture Software Developer’s Manual, Volume 1, shows the configuration of
flags in the EFLAGS register for the P6 family processors. No new flags have been added to
this register in the P6 family processors. The flags added to this register in the Pentium and
Intel486 processors are described in the following sections.
The following flags were added to the EFLAGS register in the Pentium processor:
VIF (virtual interrupt flag), bit 19.
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