Abstract: A multiprocessor computer system includes a first and second node controller, a number of processors being connected to each node controller, a memory connected to each node controller, a first input/output system connected to the first node controller, and a communications network connected between the node controllers. The first node controller includes: a crossbar unit to which are connected a memory port, an input/output port, a network port, and a plurality of independent processor ports. A first and a second processor port is connected between the crossbar unit and a first subset and a second subset, respectively, of the processors. The memory port includes a memory data port including a memory data bus and a memory address bus coupled to the first subset of memory chips, and a directory data port including a directory data bus and a directory address bus coupled to the second subset of memory chips.