Sleep mode
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Sleep 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 machine to reboot. Many devices signify this power mode by a pulsing LED power light.
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[edit] Computers
Sleep mode can go by many different names, including Stand By (Microsoft Windows 95-Server 2003), Sleep (Mac OS 8)-(Mac OS X) / (Windows Vista,Windows 7,Windows Server 2008), and Suspend (Linux). When placed in this Sleep mode, aside from the RAM which is required to restore the machine's state, the computer attempts to cut power to all unneeded parts of the machine. Because of the large power savings, most laptops automatically enter this mode when the computer is running on batteries and the lid is closed.
Though Sleep and Hibernate are generally thought as two separate functions, modern Macintoshes, Windows Vista (termed Hybrid Sleep), and some specially configured Linux machines also feature a variation of Sleep mode that incorporates the strengths of Hibernate. The RAM is copied to the hard drive before sleep mode is initiated, preserving the RAM contents in the event of a power loss.
ACPI is the current standard for power management, superseding APM and providing the backbone for sleep and hibernation on modern computers. Sleep mode corresponds to ACPI mode S3. When a non-ACPI device is plugged in, Windows will sometimes disable stand-by functionality for the whole operating system. Without ACPI functionality, as seen on older hardware, sleep mode is usually restricted to turning off the monitor and spinning down the hard drive.
[edit] Sleep Mode Testing
Because sleep mode is not the normal mode of operation, it usually is not tested as thoroughly as the normal mode. Often a device will stop working after a minute of inactivity because the sleep mode was not validated on all systems. Computer mice especially have this problem, e.g. Logitech and Microsoft mice. Even a well-designed mouse like the HP KY619AA (no sleep mode) can stop working if used with a USB card that implements a sleep mode incorrectly. Bugs in sleep mode are a serious problem if the sleep mode cannot be disabled.
In industrial machines, sleep mode is generally avoided because the costs associated with wasted time and materials far outweigh the savings in energy from sleep mode.
[edit] See also
- Green computing
- One Watt Initiative
- Linux implementations of Sleep/Suspend/Hibernate
- Hibernation Mode
[edit] Notes
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