Since then many options have been added and standards agreed upon. A machine can be in 7 power states from S0 (fully on) through S5 (powered down but plugged in) and disconnected from power (G3, Mechanical Off), with names such as "sleep", "standby", and "hibernate". In some reduced-power modes the system state is stored in RAM and the machine can "wake up" very quickly; in others the state is saved to disk and the motherboard powered down, taking at least several seconds to wake up. The machine can be awakened from a reduced-power state by a variety of signals.