Power management
Encyclopedia
Power management is a feature of some electrical appliances, especially copiers, computer
s and computer peripheral
s such as monitors
and printers
, that turns off the power or switches the system to a low-power state when inactive. In computing this is known as PC power management
and is built around a standard called ACPI
. This supersedes
APM
. All recent (consumer) computers have ACPI support.
for computer systems is desired for many reasons, particularly:
Lower power consumption also means lower heat dissipation, which increases system stability, and less energy use, which saves money and reduces the impact on the environment.
With dynamic voltage scaling
and dynamic frequency scaling
, the CPU core voltage
, clock rate
, or both, can be altered to decrease power consumption at the price of potentially lower performance. This is sometimes done in real time to optimize the power-performance tradeoff.
Examples:
Additionally, processors can selectively power off internal circuitry (power gating
). For example:
Intel VRT technology split the chip into a 3.3V I/O section and a 2.9V core section. The lower core voltage reduces power consumption.
and powers down the machine. On startup it reloads the data. This allows the system to be completely powered off while in hibernate mode. This requires a file the size of the installed RAM to be placed on the hard disk, potentially using up space even when not in hibernate mode. Hibernate mode is enabled by default in some versions of Windows
and can be disabled in order to recover this disk space.
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
s and computer peripheral
Peripheral
A peripheral is a device attached to a host computer, but not part of it, and is more or less dependent on the host. It expands the host's capabilities, but does not form part of the core computer architecture....
s such as monitors
Computer display
A monitor or display is an electronic visual display for computers. The monitor comprises the display device, circuitry, and an enclosure...
and printers
Computer printer
In computing, a printer is a peripheral which produces a text or graphics of documents stored in electronic form, usually on physical print media such as paper or transparencies. Many printers are primarily used as local peripherals, and are attached by a printer cable or, in most new printers, a...
, that turns off the power or switches the system to a low-power state when inactive. In computing this is known as PC power management
PC power management
PC power management refers to the mechanism for controlling the power use of personal computer hardware. This is typically through the use of software that puts the hardware into the lowest power demand state available...
and is built around a standard called ACPI
Advanced Configuration and Power Interface
In computing, the Advanced Configuration and Power Interface specification provides an open standard for device configuration and power management by the operating system....
. This supersedes
APM
Advanced Power Management
Advanced power management is an API developed by Intel and Microsoft and released in 1992 which enables an operating system running an IBM-compatible personal computer to work with the BIOS to achieve power management.Revision 1.2 was the last version of the APM specification, released in 1996....
. All recent (consumer) computers have ACPI support.
Motivations
PC power managementPC power management
PC power management refers to the mechanism for controlling the power use of personal computer hardware. This is typically through the use of software that puts the hardware into the lowest power demand state available...
for computer systems is desired for many reasons, particularly:
- Reduce overall energy consumption
- Prolong battery life for portable and embedded systems
- Reduce cooling requirementsComputer coolingComputer cooling is required to remove the waste heat produced by computer components, to keep components within their safe operating temperature limits.Various cooling methods help to improve processor performance or reduce the noise of cooling fans....
- Reduce noiseQuiet PCA quiet PC is a personal computer that makes little noise. Common uses for quiet PCs include video editing, sound mixing, home servers, and home theater PCs. A typical quiet PC uses quiet cooling and storage devices and energy-efficient parts....
- Reduce operating costs for energy and cooling
Lower power consumption also means lower heat dissipation, which increases system stability, and less energy use, which saves money and reduces the impact on the environment.
Processor level techniques
The power management for microprocessors can be done over the whole processor, or in specific areas.With dynamic voltage scaling
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...
and dynamic frequency scaling
Dynamic frequency scaling
Dynamic frequency scaling is a technique in computer architecture whereby the frequency of a microprocessor can be automatically adjusted "on the fly," either to conserve power or to reduce the amount of heat generated by the chip...
, the CPU core voltage
CPU core voltage
The CPU core voltage is the power supply voltage supplied to the CPU , GPU, or other device containing a processing core...
, clock rate
Clock rate
The clock rate typically refers to the frequency that a CPU is running at.For example, a crystal oscillator frequency reference typically is synonymous with a fixed sinusoidal waveform, a clock rate is that frequency reference translated by electronic circuitry into a corresponding square wave...
, or both, can be altered to decrease power consumption at the price of potentially lower performance. This is sometimes done in real time to optimize the power-performance tradeoff.
Examples:
- AMD Cool'n'QuietCool'n'QuietCool'n'Quiet is a CPU speed throttling and power saving technology introduced by AMD with its Athlon 64 processor line. It works by reducing the processor's clock rate and voltage when the processor is idle. The aim of this technology is to reduce overall power consumption and lower heat...
- AMD PowerNow!PowerNow!PowerNow! is speed throttling and power saving technology of AMD's processors used in laptops. The CPU's clock speed and VCore are automatically decreased when the computer is under low load or idle, to save battery power, reduce heat and noise...
- IBM EnergyScale
- Intel SpeedStepSpeedStepSpeedStep is a trademark for a series of dynamic frequency scaling technologies built into some Intel microprocessors that allow the clock speed of the processor to be dynamically changed by software...
- Transmeta LongRunLongRunLongRun and LongRun2 are power management technologies introduced by Transmeta. LongRun was introduced with the Crusoe processor, while LongRun2 was introduced with the Efficeon processor...
and LongRun2 - VIA LongHaulLongHaulVIA LongHaul is a CPU speed throttling and power saving technology developed by VIA Technologies. By executing specialized instructions, software can exercise fine control on the bus-to-core frequency ratio and CPU core voltage. When the system first boots, the ratio and voltage are set to...
(PowerSaver)
Additionally, processors can selectively power off internal circuitry (power gating
Power gating
This technique uses high Vt sleep transistors which cut off VDD from a circuit block when the block is not switching. The sleep transistor sizing is an important design parameter. This technique, also known as MTCMOS, or Multi-Threshold CMOS reduces stand-by or leakage power, and also enables Iddq...
). For example:
- Newer Intel CoreIntel CoreYonah was the code name for Intel's first generation of 65 nm process mobile microprocessors, based on the Banias/Dothan-core Pentium M microarchitecture. SIMD performance has been improved through the addition of SSE3 instructions and improvements to SSE and SSE2 implementations, while integer...
processors support ultra-fine power control over the functional units within the processors. - AMD CoolCore technology get more efficient performance by dynamically activating or turning off parts of the processor.
Intel VRT technology split the chip into a 3.3V I/O section and a 2.9V core section. The lower core voltage reduces power consumption.
Operating system level: Hibernation
When a computer system hibernates it saves the contents of the RAM to diskHard disk
A hard disk drive is a non-volatile, random access digital magnetic data storage device. It features rotating rigid platters on a motor-driven spindle within a protective enclosure. Data is magnetically read from and written to the platter by read/write heads that float on a film of air above the...
and powers down the machine. On startup it reloads the data. This allows the system to be completely powered off while in hibernate mode. This requires a file the size of the installed RAM to be placed on the hard disk, potentially using up space even when not in hibernate mode. Hibernate mode is enabled by default in some versions of Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
and can be disabled in order to recover this disk space.
See also
- CPU power dissipationCPU power dissipationCentral processing unit power dissipation or CPU power dissipation is the process in which central processing units consume electrical energy, and dissipate this energy both by the action of the switching devices contained in the CPU and by the energy lost in the form of heat due to the impedance...
- Low-power electronicsLow-power electronicsLow-power electronics means that the consumption of electric power is deliberately low, e.g. notebook processors.- Computing elements :The density and speed of integrated-circuit computing elements have increased exponentially for several decades, following a trend described by Moore's Law...
- Dynamic voltage scalingDynamic voltage scalingDynamic 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...
- Dynamic frequency scalingDynamic frequency scalingDynamic frequency scaling is a technique in computer architecture whereby the frequency of a microprocessor can be automatically adjusted "on the fly," either to conserve power or to reduce the amount of heat generated by the chip...
- Advanced power managementAdvanced Power ManagementAdvanced power management is an API developed by Intel and Microsoft and released in 1992 which enables an operating system running an IBM-compatible personal computer to work with the BIOS to achieve power management.Revision 1.2 was the last version of the APM specification, released in 1996....
(APM) - Advanced Configuration and Power InterfaceAdvanced Configuration and Power InterfaceIn computing, the Advanced Configuration and Power Interface specification provides an open standard for device configuration and power management by the operating system....
(ACPI)- Hibernate
- SleepSleep modeSleep mode refers to a low power mode for electronic devices such as computers, televisions, and remote controlled devices. These modes save significant electrical consumption compared to leaving a device fully on and idle, but allow the user to avoid having to reset programming codes or wait for a...
- BatteryMax (Idle Detection)BatteryMax (Idle Detection)BatteryMax is an Idle Detection System used for computer power management developed at Digital Research, Inc.'s European Development Centre in Hungerford, UK. It was invented by British borne engineers Roger Gross and John Constant in August 1989 and was first released with...
- 80 Plus80 PLUS80 PLUS is an initiative to promote energy efficiency in computer power supply units . It certifies products that have more than 80% energy efficiency at 20%, 50% and 100% of rated load, and a power factor of 0.9 or greater at 100% load....
- Energy StarEnergy StarEnergy Star is an international standard for energy efficient consumer products originated in the United States of America. It was first created as a United States government program during the early 1990s, but Australia, Canada, Japan, New Zealand, Taiwan and the European Union have also adopted...
- Green computingGreen computingGreen computing or green IT, refers to environmentally sustainable computing or IT. In the article Harnessing Green IT: Principles and Practices, San Murugesan defines the field of green computing as "the study and practice of designing, manufacturing, using, and disposing of computers, servers,...
- pmsetPmsetIn computing, pmset is a command line utility to manipulate power management settings under the Darwin and Mac OS X operating systems. It can assign sleep settings, schedule sleep and wake times, and display power information.- History :...
- PowerTOPPowerTOPPowerTOP is a software utility designed to measure, explain and minimise a computer's electrical power consumption. It was released by Intel in 2007 under the GPLv2 license...
- diagnostic tool - The Green GridThe Green GridThe Green Grid is a non-profit, open industry consortium of end-users, policy-makers, technology providers, facility architects, and utility companies collaborating to improve the resource efficiency of data centers and business computing ecosystems...
- Sleep Proxy ServiceSleep Proxy ServiceApple's Bonjour Sleep Proxy service is an open sourcecomponent of zero configuration networking, designed to assist in reducing power consumption of networked electronic devices. A device acting as a sleep proxy server will respond to Multicast DNS queries for another, compatible device which has...
- Standby powerStandby powerStandby power, also called vampire power, vampire draw, phantom load, or leaking electricity , refers to the electric power consumed by electronic and electrical appliances while they are switched off Standby power, also called vampire power, vampire draw, phantom load, or leaking electricity...
- Thermal Design PowerThermal Design PowerThe thermal design power , sometimes called thermal design point, refers to the maximum amount of power the cooling system in a computer is required to dissipate. For example, a laptop's CPU cooling system may be designed for a 20 watt TDP, which means that it can dissipate up to 20 watts of heat...
- VESA Display Power Management SignalingVESA Display Power Management SignalingVESA Display Power Management Signaling is a standard from the VESA consortium for managing the power supply of video monitors for computers through the graphics card e.g.; shut off the monitor after the computer has been unused for some time , to save power.- History :DPMS 1.0 was issued by VESA...
(DPMS)