PURPOSE: To improve the system performance by providing a shared memory space and an extended shared memory space which can be accessed by the physical address.

CONSTITUTION: Instructions and data are separated by the physical address of a processing module, and a shared memory space 200 is allocated in a space common to all processing modules, and a local main memory on each processing module is allocated in a space 100 peculiar to the processing module. The instruction code of a central processing unit in the processing module is stored in the main memory unit of the space 100 peculiar to the processing module, and only data required for sharing is stored in the shared memory module constituting the shared memory space 200. Thus, the access to the shared memory module is considerably reduced, and the number of processor modules which can be mounted on the system is increased, and as the result, the system performance is improved.