Everything about Power Management totally explained
Power management is a feature of some electrical appliances, especially
copiers,
computers and computer
peripherals such as
monitors and
printers, that turns off the power or switches the system to a low-power state when inactive. One power management standard for computers is
ACPI, which supersedes
APM. All recent (consumer) computers have ACPI support.
Motivations
Power management for computer systems are 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.
Processor level techniques
The power management for microprocessors can be done over the whole processor, or in specific areas.
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 slower performance. This is sometimes done in real time to optimize the power-performance tradeoff.
Examples:
Intel SpeedStep
AMD Cool'n'Quiet
AMD PowerNow!
VIA LongHaul (PowerSaver)
Transmeta LongRun and LongRun2
Newer Intel Core processors support ultra-fine power control over the function units within the processors.
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 computer system hibernates it saves the contents of the RAM to disk 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.
Further Information
Get more info on 'Power Management'.
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