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MOVD            Move Doubleword to/from MMX Register

MOVD destination, source                             CPU: MMX

        Logic   if destination = mm
                   mm(63..0) <- ZeroExtend(r/m32)
                else
                   r/m32 <- mm(31..0)
                endif

    MOVD copies 32 bits from the source operand to the destination
    operand.
    The destination and source operands can be either MMX registers,
    32-bit memory operands, or 32-bit integer registers. MOVD cannot
    transfer data from an MMX register to an MMX register, from memory
    to memory, or from an integer register to an integer register. 

    When the destination operand is an MMX register, the 32-bit source
    operand is written to the low-order 32 bits of the 64-bit destination
    register. The destination register is zero-extended to 64 bits. 

    When the source operand is an MMX register, the low-order 32 bits of
    the MMX register are written to the 32-bit integer register or 32-bit
    memory location.


    Opcode      Format
    0F 6E /r    MOVD mm, r/m32
    0F 7E /r    MOVD r/m32, mm