Sleep

Sleep mode is a low power state in which a Macintosh computer powers down the display and suspends drive activity. It is somewhat like Shut Down, except that the contents of memory are preserved so the computer can be ready more quickly when awoken from sleep.

Description
Sleep mode does continue using some battery power for RAM. It is possible, on laptops, to put a computer to sleep for a long time and lose all remaining battery charge.

To wake a Mac up, press a key or move the mouse. If a laptop has slept and needs waking, open its case and, if needed, press a key.

On Windows laptops, "hibernation" mode does not utilize any power, but time is expended to write and then re-read memory contents from the drive upon waking the computer each time. MacBooks call this standby mode and use a faster process called safe sleep.

History
Sleep was an option from the very first Macintosh Portable, and remained in the laptops-only realm until the 1995 introduction of the PCI-based Power Macintosh computers. Today, all Macs can sleep normally.

Sleep versus restart
Restarting a Mac (notably an iBook or PowerBook) is only needed in the following circumstances:


 * Upon the installation or removal of an AirPort card or AirPort Extreme card;
 * Upon the insertion of a PowerBook Duo into a Duo Dock;
 * If the user wishes to use Mac OS 9 instead of Mac OS X (or the other way round);
 * If the user wishes to start with different extensions, control panels and startup items (classic Mac OS only);
 * Upon the attachment or removal of an external monitor (this applies only with very old laptops, and does not apply to newer portables, such as all iBooks, MacBooks, and more recent PowerBooks);
 * Upon the attachment of a laptop to desktop in target disk mode.