NASM 2.05 based x86 Instruction Reference[ch042]
A.5.23 CMOVcc: Conditional Move CMOVcc reg16,r/m16 ; o16 0F 40+cc /r [P6] CMOVcc reg32,r/m32 ; o32 0F 40+cc /r [P6] CMOV moves its source (second) operand into its destination (first) operand if the given condition code is satisfied; otherwise it does nothing. For a list of condition codes, see section A.2.2. Although the CMOV instructions are flagged P6 and above, they may not be supported by all Pentium Pro processors; the CPUID instruction (section A.5.34) will return a bit which indicates whether conditional moves are supported.