Dennard scaling
Robert Dennard (IBM, 1974): as transistors shrink proportionally, voltage + power density drops — faster chips without getting hotter.
Drove Intel's "tick-tock" strategy 1974–2005. Died around 2006 at 65nm — leakage currents dominate, voltage can't drop further without logic errors. Consequence: "frequency scaling" stopped at ~3.5 GHz, focus shifted to multi-core. "Dark silicon" effect: at 5nm only ~25 % of transistors can be powered simultaneously without thermal overload.