Dennard scaling

Dennard scaling is the principle that shrinking transistor dimensions and operating voltage together can keep power density roughly constant while increasing transistor density and speed.

Constant-field scaling: A scaling model in which transistor dimensions and operating voltages shrink proportionally, keeping internal electric fields roughly constant. It states the idealized rules behind Dennard scaling.
Robert Dennard: An IBM electrical engineer who coauthored the 1974 paper establishing transistor scaling rules. His name became attached to the constant-power-density scaling principle.
Power wall: The limit on processor performance imposed by power consumption and heat dissipation. Once voltage stopped scaling, rising transistor counts pushed chips toward this limit.
Koomey's law: The observation that the number of computations per joule has historically doubled at a regular pace. It tracks energy efficiency rather than Dennard's transistor power-density relationship.
Subthreshold leakage: Current that flows through a transistor below its nominal threshold voltage. It rises sharply when threshold voltage is reduced to preserve scaling benefits.
MOSFET: A voltage-controlled transistor that uses an electric field to regulate current through a semiconductor channel. Dennard's scaling rules were developed for this transistor type.
Dennard scaling paper: The 1974 paper by Robert Dennard and colleagues describing scaling laws for MOSFETs. It presented the assumptions and relationships underlying the principle.
CPU clock rate: The frequency at which a processor's clock coordinates operations. Clock-rate growth slowed as voltage and power could no longer scale as before.
CMOS scaling: The reduction of dimensions in complementary metal–oxide–semiconductor devices and circuits. Physical CMOS scaling continued after the ideal power-scaling relationship weakened.
Interconnect delay: The time required for electrical signals to propagate through wires connecting circuit elements. Wiring increasingly limits performance even when transistors become smaller.

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