Network, Computer and Programming Resources

Instruction mmx - PSUBUSB/PSUBUSW—Packed Subtract Unsigned with Saturation

Subtracts the individual unsigned data elements (bytes or words) of the source operand (second operand) from the individual unsigned data elements of the destination operand (first operand). If the result of an individual subtraction exceeds the range for the specified unsigned data type, the result is saturated. The destination operand musts be an MMX technology register; the source operand can be either an MMX technology register or a quadword memory location. The PSUBUSB instruction subtracts the unsigned bytes of the source operand from the unsigned bytes of the destination operand and stores the results to the destination operand. When an individual result is less than zero (a negative value), the saturated unsigned byte value of 00H is written to the destination operand. The PSUBUSW instruction subtracts the unsigned words of the source operand from the unsigned words of the destination operand and stores the results to the destination operand. When an individual result is less than zero (a negative value), the saturated unsigned word value of 0000H is written to the destination operand.