A method for a byte swap operation on a 64 bit operand. The method of one embodiment comprises accessing an operand stored in a register. The operand is comprised of a plurality of bytes of data. A first set of bytes located in an upper half of said register is reordered. A second set of bytes located in a lower half of said register is reordered. The first set of bytes is swapped with the second set of bytes, wherein the first set of bytes is relocated to the lower half of the register and the second set of bytes is relocated to the upper half of the register.