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Instruction mmx - PMULHW—Packed Multiply High

Multiplies the four signed words of the source operand (second operand) by the four signed words of the destination operand (first operand), producing four signed, doubleword, intermediate results. The high-order word of each intermediate result is then written to its corresponding word location in the destination operand. The destination operand must be an MMX technology register; the source operand may be either an MMX technology register or a 64-bit memory location.