A three-dimensional mesh multiprocessor system using board-to-board free-space optical interconnects: COSINE-III

A prototype multiprocessor system using board-to-board free-space optical interconnects distributed over the processor boards is constructed for the first time. The system consists of 64 processing units interconnected in a three-dimensional (3D) mesh network with the help of bi-directional free-space optical interconnects. Theoretical analysis of signal delay and wiring congestion characteristics in the 3-D mesh network using free-space optical interconnects concludes that the network is superior to that using a conventional backplane interconnects. In the prototype system, signal transmission of all 96 free-space optical interconnects is stable even after repeated extraction and insertion of the processor boards, and system operation without error for 100 h is performed. The system is also shown to be easy to extend to a larger and more flexible system