Inside the Machine

Power Density

The amount of power that a chip dissipates per unit area is called its power density, and there are two types of power density that concern processor architects: dynamic power density and static power density.

Dynamic Power Density

Each transistor on a chip dissipates a small amount of power when it is switched, and transistors that are switched rapidly dissipate more power than transistors that are switched slowly. The total amount of power dissipated per unit area due to switching of a chip’s transistors is called dynamic power density. There are two factors that work together to cause an increase in dynamic power density: clockspeed and transistor density.

Increasing a processor’s clockspeed involves switching its transistors more ...