Dynamic voltage scaling  Dynamic voltage scaling is a power management technique in computer architecture, where the voltage used in a component is increased or decreased, depending upon circumstances. Dynamic voltage scaling to increase voltage is known as overvolting; dynamic voltage scaling to decrease voltage is known as undervolting. Undervolting is done in order to conserve power, particularly in laptops and other mobile devices, where energy comes from a battery and thus is limited, or in rare cases, to increase reliability. Overvolting is done in order to increase computer performance. The term "overvolting" is also used to refer to increasing static operating voltage of computer components to allow operation at higher speed (overclocking). MOSFET-based digital circuits operate using voltages at circuit nodes to represent logical state. The voltage at these nodes switches between a high voltage and a low voltage during normal operation—when the inputs to a logic gate transition, the transistors making up that gate may toggle the gate's output. At each node in a circuit is a certain amount of capacitance. Capacitance can be thought of as a measure of how long it takes for a given current to produce a given voltage change. The capacitance arises from various sources, mainly transistors (primarily gate capacitance and diffusion capacitance) and wires (coupling capacitance). Toggling a voltage at a circuit node requires charging or discharging the capacitance at that node; since currents are related to voltage, the time it takes depends on the voltage applied. By applying a higher voltage to the devices in a circuit, the capacitances are charged and discharged more quickly, resulting in faster operation of the circuit and allowing for higher frequency operation. Many modern components allow voltage regulation to be controlled through software (for example, through the BIOS). It is usually possible to control the voltages supplied to the CPU, RAM, PCI, and PCI Express (or AGP) port through a PC's BIOS. However, some components do not allow software control of supply voltages, and hardware modification is required by overclockers seeking to overvolt the component for extreme overclocks. Video cards and motherboard northbridges are components which frequently require hardware modifications to change supply voltages. These modifications are known as "voltage mods" in the overclocking community. Undervolting is reducing the voltage of a component, usually the processor, reducing temperature and cooling requirements, and possibly allowing a fan to be omitted. The "switching power" dissipated by a chip using static CMOS gates is formula_1, where C is the capacitance being switched per clock cycle, V is the supply voltage, and f is the switching frequency, so this part of the power consumption decreases quadratically with voltage.