Power management techniques for computer systems and processors typically use dynamic voltage and frequency scaling. Reducing frequency allows reducing voltage, which improves efficiency. However, practical circuits have a minimum operating voltage, Vmin, and cannot operate below Vmin. At Vmin operation, typically there is also a most-efficient frequency, Fmin. Speed can be reduced below Fmin to reduce power, but speed drops faster than power, so efficiency suffers. Another technique includes software-generated requests for idle states, without direct control of voltage, other hardware parameters, and without a guarantee of the physical state that will result. The operating system is typically the software that generates the requests for idle states.
Furthermore, widespread use of computer systems for an ever-broader range of tasks, combined with software inefficiencies, and its requirements of hardware, have also caused an increase in computing device energy consumption. In fact, some studies indicate that computing devices consume a sizeable percentage of the entire electricity supply for a country, such as the United States of America. As a result, there is a vital need for energy efficiency and conservation associated with integrated circuits. These needs will increase as servers, desktop computers, notebooks, Ultrabooks™, tablets, mobile phones, processors, embedded systems, etc. become even more prevalent (from inclusion in the typical computer, automobiles, and televisions to biotechnology).