1. A shared-memory computer system having a plurality of coupled processing nodes, each processing node having a processor for executing software instructions, and a main memory portion of a global shared memory space organized in pages, each page having a plurality of respectively addressed data items, the computer system comprising: a plurality of home processing nodes assigned from the plurality of processing nodes, each data item in the global shared memory space assigned to a home processing node based on the address of the respective data item; for a data item in the global shared memory space, a master processing node from the plurality of processing nodes wherein a current copy of the data item is stored, there being at least one data item in the global shared memory space having its home processing node different from its master processing node; and for each home processing node, a home directory memory located at the home processing node for centralizing directory information for each data item assigned to the home processing node.