Performance Driven Low Skew Clock Distribution on Multichip Modules.

A performance driven low skew system clock distribution on multichip modules (MCMs) is described from a systems perspective by considering system bandwidths, required system switching energies, number of fanout nodes supported and the flexibility of the network structure to accommodate placement/routing requirements of various integrated circuits on the MCM. Electrical and optical interconnection technologies are considered and compared to design a clock distribution network which can meet the various system performance requirements. Electrical H-tree networks modeled as transmission lines are designed and evaluated along with guided wave optical H-tree networks. A performance comparison between electrical and optical approaches suggests that the optical H-tree clock distribution network has a superior capability compared to the electrical one by providing large bandwidth, large fanout, small system switching energy and flexible network configuration. Thus optical system clock distribution for MCM is preferred (and, possibly, required) for a high speed, MCM-based and synchronous distributed multiprocessor computer system (DMCS), particularly above 300 MHz. The system performance analysis of the optical clock distribution network demonstrate the feasibility of this approach and also show that the achievable clock speed is limited by the laser diode source and photodiode receivers, and not by optical waveguide distribution network.