A multiprocessor system includes first and second processors and a multi-path accessible semiconductor memory device including a shared memory area and a pseudo operation execution unit. The shared memory area is accessible by the first and second processors according to a page open policy. The pseudo operation execution unit responds to a virtual active command from one of the first and second processors to close a last-opened page. The virtual active command is generated with a row address not corresponding to any row of the shared memory area. For example, bit-lines of a last accessed row are pre-charged for closing the last-opened page.