Abstract: A technique for providing a compare-and-exchange (CMPXCHG) instruction which may be implemented in an instruction set requiring a limited number of source and destination operands for each instruction in the instruction set. In order to utilize an instruction to perform a read-modify-write operation three source and one destination operands are needed to supply the location of various information used in executing the instruction. Instead of providing all four operands with the instruction, the CMPXCHG instruction of the present invention utilizes an implied operation-specific register. This register is implied in the instruction when the CMPXCHG instruction is executed, so that only two source operands are needed with the CMPXCHG instruction.