Mac OS X: Why your Mac might not sleep or stay in sleep mode
Learn why your Mac might not go to sleep when you expect it to, or why it might not stay in sleep mode.
What's sleep mode? It's a low power, energy-saving feature that offers both environmental and economic benefits, as well as helping to extend the life of batteries and displays.
There are reasons why you may want your Mac to stay awake even though you are not using the keyboard or mouse, such as when you are:
- Watching a DVD movie
- Listening to your iTunes music library
- Running an automated backup
- Away from your computer while downloading large files
Note: For troubleshooting tips, go to the "How can I determine what is causing a sleep issue and how can I resolve it?" section at the bottom of this article.
Different ways to put the computer to sleep
- From the Apple menu, choose Sleep.
- Press the computer's Power button--you may have to click Sleep after pressing the Power button.
- Close the display of a portable computer.
- Leave the system inactive for the amount of time specified in the Energy Saver preferences.
- Schedule sleep to occur at a specific time of day in the Energy Saver pane of System Preferences.
- If you have a Macintosh computer with an infrared (IR) receiver, you can put your computer to sleep using an Apple Remote. Hold the Play/Pause button on the remote until the computer goes to sleep. When your computer is in sleep, pressing any button on the remote will wake the computer.
About different kinds of sleep in Energy Saver preferences
Hard disk sleep: When the hard drive is inactive for a period of time, it will stop spinning to conserve energy. Other than a slight reduction in sounds from the computer, you probably will not notice when the hard disk is sleeping. The hard disk will start spinning the next time information needs to be read from or written to the disk, and you may notice a brief delay as this occurs.
Display sleep: When display sleep occurs, the display will go black, but running applications remain active. If your display has a power indicator, it may change to indicate that the display is in a low-power mode. To wake the display, simply move the mouse, touch the trackpad, or press a key on the keyboard.
System sleep: Usually referred to as "sleep," when the system goes to sleep the computer (as well as the hard disk and display) will enter a low-power state. The power indicator on the computer will pulsate, flash or turn amber (depending on your Mac). To wake the computer, press a key on the keyboard, click a mouse button, connect or disconnect a USB device, or open the lid if it's a portable Mac.
Note: Hard disk activity does not prevent display sleep, but it does prevent system sleep. It is not uncommon for the display to sleep before the system goes to sleep if both types of sleep are set to occur after the same length of inactivity.
Why doesn't the computer go to sleep at the expected time based on Energy Saver settings?
You can configure Energy Saver preferences to set your computer to automatically sleep after a specified period of time; an internal counter called a "sleep timer" monitors the amount of time your computer has been inactive. When the counter's time matches the amount of time you specified, the computer enters sleep mode and displays a pulsing power light.
Some things reset the sleep timers, preventing the computer from sleeping:
- Hard drive access (even if you're not using the computer, a running application might be accessing your drive, such as when downloading a large file or listening to music in iTunes)
- Moving the mouse or using a portable Mac's trackpad, pressing a mouse button, or pressing a key on the keyboard
- Some System Preferences settings (see below)
- Open applications (see below)
- Input devices (see below)
- Expansion cards (see below)
- Additional drives, such as USB, FireWire, DVD, or CD drives (see below)
Some System Preferences settings affect sleep
Energy Saver is a System Preference that can help you optimize energy settings as well as sleep times and processor usage. Note that processor controls are not used for Intel-based Macs because they have built-in power-saving features. Only PowerPC-based Macs display processor controls.
In these situations, the display will sleep (unless Energy Saver preferences is configured to never let the display sleep) but the processor will stay awake and the power light will remain on:
You can allow Bluetooth devices to wake a sleeping computer by enabling "Allow Bluetooth devices to wake this computer" in Bluetooth preferences. A bluetooth device paired correctly should not typically prevent a computer from sleeping. However, some Bluetooth mice can interfere with sleep
Your computer will not sleep if Spotlight is indexing content, because that requires hard disk access. For example, if you just installed or reinstalled Mac OS X, Spotlight may need a while to index content.
If you are sharing files, an Internet connection, a printer, and so forth, sleep can be affected. You might want to consider setting the Energy Saver sleep timer to "Never" so that sharing services are not disrupted.
Keyboard, mouse, other input devices can affect sleep
Keyboard presses and mouse button clicks can wake a sleeping computer. Mouse movement alone will only wake a sleeping display. Even though your Mac may be in sleep mode, it remains aware of keyboard presses and mouse clicks.
Open applications can affect sleep
Software that accesses the hard drive will delay sleep mode until it is either quit or done accessing the drive. For example:
- Songs playing in iTunes.
- A movie disc playing in DVD Player.
However, this can also occur in subtle ways you might not expect:
- If an application uses a custom font to display text but the font resource is marked purgeable, then at some point the memory manager will purge the font from memory. When the application tries to draw text using that font again, it will be loaded from the hard drive, resetting the sleep timer.
- Applications can be designed to keep the system awake and prevent idle sleep indefinitely. In developer lingo, an application may explicitly prevent system sleep by calling IORegisterForSystemPower(), and calling IOCancelPowerChange() when it receives a power management kIOMessageCanSystemSleep notification.
Expansion cards can affect sleep
Some PCI expansion cards can prevent sleep. A card's Mac OS X driver may not allow the computer to remove power from it, preventing the system from entering full sleep. Instead, the system enters a state named "Doze".
Some kinds of PCI cards prevent any kind of sleep mode--your system will not go into low-power mode during long periods of inactivity. The computer fans may run excessively when this is the case.
Other hard drives or optical media drives can affect sleep
If there is disk access activity at least once a minute--on disks such as ATA drives, FireWire drives, optical media drives, or USB drives--the computer will not idle sleep.
How can I determine what is causing a sleep issue and how can I resolve it?
These are the most likely causes and solutions for sleep issues:
- Sharing preferences: Enabling sharing for any connections can potentially disable sleep. Turn off file sharing if it's not being used.
- Bluetooth settings: Bluetooth can wake your computer if you set the "Allow Bluetooth devices to wake this computer" checkbox in Bluetooth System Preferences.
- Are a keyboard and mouse connected and working correctly?
- Do you have any other external USB or FireWire devices connected? Try removing or disconnecting them one by one, when not in use, taking care to dismount any that are storage devices before disconnecting them.
- Do you have a print job in the Printer Queue? Remove any print jobs that are in the queue.
- Is Spotlight indexing? This can take anywhere from several minutes to several hours after a new installation, or after connecting a storage device which contains unindexed data. Indexing prevents idle sleep.
- Additional Software: Try a Safe Boot to help isolate a software issue.
- Put your ear near your computer. Do you hear the "clicking" sounds of hard disk access?
- Energy Saver settings: If the computer and display sleep timers are set to "Never", the computer will not sleep.