Multiprocessor system with distributed shared memory having hot plug function for main memories

A multiprocessor system of a distributed shared memory structure having a plurality of nodes each comprising at least one processor, an IO unit, a main memory, and a system control unit, said system control unit comprising a routing control unit, a memory control unit, an inter-node interface control unit, a lock control unit, and a mover;

• said routing control unit having means for being supplied with a memory access request issued from said processor, said IO unit, or said mover, determining which node the memory access request is destined for the main memory in, adding routing information to the memory access request, and transferring the memory access request to said inter-node interface control unit;
• said inter-node interface control unit having means for, if the memory access request transferred from said routing control unit is destined for the main memory of another node, issuing a memory access request to said other node via a system bus, and, if a memory access request other than a locked or unlocked memory access request received from said routing control unit or the system bus is destined for the main memory of its own node, transferring a lock address buffer index request to said lock control unit, and, if said lock control unit indicates that a transferred address is not locked, transferring the memory access request via said memory control unit to said main memory, and, if said lock control unit indicates that the transferred address is locked, holding the memory access request and transferring a memory access request address again to said lock control unit, and repeating the above process until the memory access request address is unlocked, and means for, if the memory access request transferred from said routing control unit or the system bus is a locked memory read request destined for its own node, transferring a lock request to said lock control unit, if an indication of locking success is received from said lock control unit, transferring the memory read request to said memory control unit, if an indication of locking failure is received from said lock control unit, eliminating the locked memory read request, and if the memory access request transferred from said routing control unit or the system bus is an unlocked memory write request destined for its own node, transferring the memory write request to said memory control unit, and transferring an unlock request to said lock control unit;
• said lock control unit having means for determining whether the transferred address is locked or not when said lock address buffer index request is transferred, and indicating the determined result to said inter-node interface control unit, and, if the address of said lock request is unlocked, locking said address and sending an indication of locking success to said inter-node interface control unit, and, if the address of said lock request is locked, sending an indication of locking failure to said.inter-node interface control unit and a lock bus, and unlocking the address of said unlock request when said unlock request is received.