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19-6 Vol. 3
ARCHITECTURE COMPATIBILITY
19.13.1 Instructions Added Prior to the Pentium Processor
The following instructions were added in the Intel486 processor:
• BSWAP (byte swap) instruction.
• XADD (exchange and add) instruction.
• CMPXCHG (compare and exchange) instruction.
• ΙNVD (invalidate cache) instruction.
• WBINVD (write-back and invalidate cache) instruction.
• INVLPG (invalidate TLB entry) instruction.
The following instructions were added in the Intel386 processor:
• LSS, LFS, and LGS (load SS, FS, and GS registers).
• Long-displacement conditional jumps.
Table 19-1. New Instruction in the Pentium Processor and
Later IA-32 Processors
Instruction CPUID Identification Bits Introduced In
CMOVcc (conditional move) EDX, Bit 15 Pentium Pro processor
FCMOVcc (floating-point conditional
move)
EDX, Bits 0 and 15
FCOMI (floating-point compare and set
EFLAGS)
EDX, Bits 0 and 15
RDPMC (read performance monitoring
counters)
EAX, Bits 8-11, set to 6H;
see Note 1
UD2 (undefined) EAX, Bits 8-11, set to 6H
CMPXCHG8B (compare and exchange 8
bytes)
EDX, Bit 8 Pentium processor
CPUID (CPU identification) None; see Note 2
RDTSC (read time-stamp counter) EDX, Bit 4
RDMSR (read model-specific register) EDX, Bit 5
WRMSR (write model-specific register) EDX, Bit 5
MMX Instructions EDX, Bit 23
NOTES:
1. The RDPMC instruction was introduced in the P6 family of processors and added to later model
Pentium processors. This instruction is model specific in nature and not architectural.
2. The CPUID instruction is available in all Pentium and P6 family processors and in later models of
the Intel486 processors. The ability to set and clear the ID flag (bit 21) in the EFLAGS register
indicates the availability of the CPUID instruction.