MULTIPLEX SHARED MEMORY CONTROL SYSTEM, MULTIPLEX SHARED MEMORY SYSTEM, AND SHARED MEMORY EXTENSION SYSTEM

摘要

PURPOSE:To ensure the excellent performance, a low cost, and the excellent connection properties to the CPUs of different models by securing such constitution where the 3rd one of three CPUs has no shared memory and giving an access to at least one of the 1st and 2nd CPUs of the 1st and 2nd CPUs when a memory read request is produced. CONSTITUTION:Each of 1st and 2nd CPU 1 and 2 out of three CPUs contains at least one of two shared memories GM and gives an access to the shared memory of its own CPU when a shared memory read request is received. The 3rd CPU 3 has no shared memory GM and gives an access to at least one of two memories GM contained in both CPU 1 and 2 with a shared memory read request. Thus it is not required for all CPUs to contain the shared memories of the same capacity in terms of a multiplex shared memory. As a result, the best balance is secured between the performance and the cost. In addition, the excellent interchangeability is ensured among plural CPUs.