The transition predated the eighties, at least among the significant innovators. Remember What the Dormouse Said.
The initial explosion I mentioned was east coast, not west. Univac, Burroughs, RCA, IBM, Sperry, etc, etc. All the big shops were east coast.
The significance of Silicon Valley is overstated. East coast had Commodore, Rockwell, Carnegie Mellon. The west coast had some neat stuff, true, but near every thing of size happened more and earlier east coast.