Michael Steinberger, Lead Architect, Serial Channel Products, SiSoft
Paul Wildes, Consulting Engineer, Sack Brothers Enterprises, L.L.C.
Eric Brock, Principal Member of Technical Staff, SiSoft
Walter Katz, Lead Architect, SiSoft

IIn system level measurements, the paths with the worst bit error rate were not the longest paths, but rather some of the paths that had a short length of transmission line between two connectors. Even within this class of paths, however, there was no easy way to predict which paths would be bad. Subsequent post-route analysis demonstrated that the problem was multiple reflections between the connectors, but that the problem was detected only when their timing was exactly wrong.

This paper presents the analysis methods and results, and recommends unequalizable energy as a reliable metric for identifying potential problem paths.