Electrical characteristics of lossy interconnections for high-performance computer applications

Abstract

This paper discusses the maximum usable length (ℓmax) for high-speed pulse propagation, and its dependence on signal line resistance (R) for a range of wiring technologies. As an example, we present results from measurements and analyses of experimental interconnection structures and their agreement is highlighted. The analysis is based on a transmission line model which includes frequency-dependent losses such as skin-effect and dielectric dispersion. The paper addresses the problems found on lossy lines, such as reflections, rise-time slow down, increased delay, attenuation, and crosstalk. A wide bandwidth test system that relies on novel high frequency and high impedance coaxial probes, which was developed to characterize our test structures, is described. The limiting factors that affect circuitto-circuit path delays in high-performance computers are then discussed and guidelines are given for maintaining distortion-free propagation of high-speed signals. Simulations of resistive interconnections in a practical digital environment are presented.