Waking up your MacBook from sleep

When we put our MacBooks to sleep, we hope that they will wake. Please! And we when we want them to go to sleep, we hope that they will slumber. But it always doesn't work that way.
Written by David Morgenstern, Contributor
When we put our MacBooks to sleep, we hope that they will wake. Please! And we when we want them to go to sleep, we hope that they will slumber. But it always doesn't work that way. When running under Mac OS X Tiger (10.4), I occasionally encountered problems getting my MacBook Pro to wake from sleep. I found the following procedure helps: 1. Before I put the machine to sleep, I unplug anything connected, such as an Ethernet cable, hard drive or mouse. 2. Next I use the Sleep command under the Apple Menu to put the MacBook to sleep and I wait until the screen actually goes blank before closing the lid. I don't just close the lid. 3. When I go to wake the MacBook, I open the machine and make sure that I don't plug anything into the machine before I wake it. I've continued this process under Mac OS X Leopard and have had no further trouble with waking from sleep. The Energy Saver control panel defines several kinds of sleep: "computer sleep," which is what we commonly think of as sleep, where the system sleeps; "display sleep," where the screen goes black; and "hard disk" sleep, where the drive spins down. According to developer Patrick Stein, the author of the free SmartSleep preference pane, there are three sleep modes that your Mac can use:

Sleep, where the Mac saves the state in RAM, which means it can go to sleep and wake up quickly, but could bring trouble if the battery runs down or is removed. Hibernate, where the state is written to the hard disk (the safest for your data), but takes the longest time to be put to sleep and to wake up. Combination Sleep and Hibernate, which Apple calls Safe Sleep. It may take the longest time to sleep but it also can wake quickly. And if your MacBook supports it, you can swap in a fresh battery. Stein's SmartSleep lets you choose between the modes. On the other hand, there can be problems when putting your MacBook to sleep. The Apple Support note Why your Mac might not sleep or stay in sleep mode offers some suggestions as well as a troubleshooting guide.
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
In the note, I was interested to see that a Bluetooth setting can also interfere with sleep.
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.
Applications can also affect sleep, even some small things.
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.
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