Power
The switching power dissipated by a chip using static CMOS gates is C·V2·f, 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. The formula is not exact however, as many modern chips are not implemented using 100% CMOS, but also use special memory circuits, dynamic logic such as domino logic, etc. Moreover, there is also a static leakage current, which has become more and more accentuated as feature sizes have become smaller (below 90 nanometres) and threshold levels lower.
Accordingly, dynamic voltage scaling is widely used as part of strategies to manage switching power consumption in battery powered devices such as cell phones and laptop computers. Low voltage modes are used in conjunction with lowered clock frequencies to minimize power consumption associated with components such as CPUs and DSPs; only when significant computational power is needed will the voltage and frequency be raised.
Some peripherals also support low voltage operational modes. For example, low power MMC and SD cards can run at 1.8 V as well as at 3.3 V, and driver stacks may conserve power by switching to the lower voltage after detecting a card which supports it.
When leakage current is a significant factor in terms of power consumption, chips are often designed so that portions of them can be powered completely off. This is not usually viewed as being dynamic voltage scaling, because it is not transparent to software. When sections of chips can be turned off, as for example on TI OMAP3 processors, drivers and other support software need to support that.
Read more about this topic: Dynamic Voltage Scaling
Famous quotes containing the word power:
“Do not withhold good from those to whom it is due, when it is in your power to do it.”
—Bible: Hebrew, Proverbs 3:27.
“Relying ... on the patronage of your good will, I advance with obedience to the work, ready to retire from it whenever you become sensible how much better choice it is in your power to make.”
—Thomas Jefferson (1743–1826)
“The power we exert over the future behavior of our children is enormous. Even after they have left home, even after we have left the world, there will always be part of us that will remain with them forever.”
—Neil Kurshan (20th century)