First 3D silicon stack I saw was in the late 80s. (Back then it was a stack of 2.) The field has produced a rich string of PR announcements and funding propos

First 3D silicon stack I saw was in the late 80s. (Back then it was a stack of 2.) The field has produced a rich string of PR announcements and funding proposals over that time though. The problems then as now: Heat dissipation and signal integrity as you pass through the stack.