Much of high performance technical computing has moved from shared memory architectures to message based cluster systems. The development and wide adoption of the MPI parallel programming model has hastened this transition. Parallel scaling, however, is frequently limited by the inefficient communication hardware commonly found in commodity based clusters. This paper describes a new communication network (the SiCortex fabric) employed in the SiCortex SC5832 integrated cluster system. The fabric switch and communications controller are integrated with a single-chip multiprocessor node and provides three pointto-point links per node chip. The resulting design provides low latency, high bandwidth, reliable communication between the 972 nodes of the SiCortex system.