Dark silicon
In the electronics industry, dark silicon is the amount of circuitry of an integrated circuit that cannot be powered-on at the nominal operating voltage for a given thermal design power (TDP) constraint. Dennard scaling would posit that as transistors get smaller, they become more efficient in proportion to the increase in number for a given area, but this scaling has broken down in recent years, meaning that increases in the efficiency of smaller transistors are not proportionate with the increase in their number.