Towards a comparison between chip-level optical interconnection and board-level exterconnection

A preliminary comparison between two time-of-flight (ToF)-limited interconnect technologies, chip-level guided-wave optical interconnection and board-level electrical exterconnection, is presented. For a 20 megacell single-cycle chip architecture integrating 4.1 billion transistors implemented in 45 nm technology on a 572 mm/sup 2/ die, it is found that all global interconnects of length greater than 32 mm could be replaced by optical waveguides with embedded air-gap cladding regions to allow a ToF-limited global clock frequency of 4.4 GHz. In the case of off-chip exterconnection, all interconnects of length greater than 36 mm could be replaced to enable a ToF-limited frequency of 4.0 GHz.