Article intended for FPGA-types has a nice summary (for dummies like me) of the state of the wire-delay/interconnect problem:
"James Meindl at the Georgia Institute of Technology, who has become an expert in predicting the impending impact of physical parameters on future IC generations, has taken on the interconnect problem. His analysis predicts 80 levels of metal by 2014 if no architectural changes are made in circuit design."
Won't happen of course. Possible solutions: get away from Manhattan routing (25% savings in wire delay--yawn), copper interconnect (been done of course, discovered from the same article that copper atoms like to diffuse into silicon, maybe it's just as well that chips become obsolete every few years), repeaters every few atoms or so (why do we keep trying to do it with electrons? Because we're *electrical* engineers, that's why), and then
"Another possibility in this direction is the introduction of photonic waveguides for long interconnect lines. There is some hope here. With recent work on building photonic bandgap structures into silicon circuits, this might become a practical option for designers. Photonic structures can now be defined on-chip with the same lithographic processes used in CMOS manufacturing. Photonic interconnects do not carry the RC delay penalty that creates so many problems for wire inter connects."
RM