[gjm11]

> let's assume it's about 1mm per pico-second (3 times that of vacuum).

If Intel had found a way of making signals propagate three times faster than the speed of light in vacuum, everyone would be too busy rewriting the laws of physics to take notice of their transistor technology improvements.

A 3mm path-length difference would be more like 10ps; 20ps for a 2x3mm round trip.

(But I bet Intel take a lot of trouble to reduce those distances. There probably isn't anything that has to happen in a single cycle that involves 6mm-worth of propagation delays.)