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Instruction mmx - PSUBSB/PSUBSW—Packed Subtract with Saturation

Subtracts the individual signed data elements (bytes or words) of the source operand (second operand) from the individual signed data elements of the destination operand (first operand). If the result of a subtraction exceeds the range for the specified data type, the result is saturated. The destination operand must be an MMX technology register; the source operand can be either an MMX technology register or a quadword memory location. The PSUBSB instruction subtracts the signed bytes of the source operand from the signed bytes of the destination operand and stores the results to the destination operand. When an individual result is beyond the range of a signed byte (that is, greater than 7FH or less than 80H), the saturated byte value of 7FH or 80H, respectively, is written to the destination operand. The PSUBSW instruction subtracts the signed words of the source operand from the signed words of the destination operand and stores the results to the destination operand. When an individual result is beyond the range of a signed word (that is, greater than 7FFFH or less than 8000H), the saturated word value of 7FFFH or 8000H, respectively, is written to the destination operand.