Abstract: Disclosed is an apparatus and method for providing synchronization support in a multiprocessor environment using a memory interface that supports an atomic read-modify-write operation as well as conventional read and write access to memory. Selection of the operation is made dependent on which ever address of a plurality of addresses is used to reference a single physical memory location in which there is stored a lock variable used to restrict access to a shared resource. When the particular access corresponds to a read-modify-write operation, the lock variable is read out and a modified version written back into memory on the condition that the shared resource is available to the requesting processor. The method and apparatus executes read-modify-write operations by interface logic circuitry in response to a single processor read operation. Through these atomic or otherwise indivisible operations, the method and apparatus precludes multiprocessor conflict.