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Instruction mmx - PMADDWD—Packed Multiply and Add

Multiplies the individual signed words of the destination operand by the corresponding signed words of the source operand, producing four signed, doubleword results. The two doubleword results from the multiplication of the high-order words are added together and stored in the upper doubleword of the destination operand; the two doubleword results from the multiplication of the low-order words are added together and stored in the lower doubleword of 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. The PMADDWD instruction wraps around to 80000000H only when all four words of both the source and destination operands are 8000H.