When the computer goes into sleeping mode, its behavior depends on a power management variable called hibernate mode. The hibernate mode can be set to different values:
• 0 (quick): Default sleep behavior on most Apple computers. RAM is still powered on while sleeping. Wake up is fast. Safe sleep is disabled.
• 1 (deep): Hibernation behavior. System is totally shut down while sleeping. RAM contents are dumped to disk. Wake up is slow.
• 3 (safe): Default behavior on Powerbook HD and later computers. RAM is still powered on while sleeping. Wake up is fast. Safe sleep is enabled, so RAM contents are also dumped to disk before going to sleep.
• 5 (deep): Same as mode 1 for systems with encrypted virtual memory.
• 7 (safe): Same as mode 3 for systems with encrypted virtual memory.
Only a single mode can be activated at a time. In order to check what hibernate mode is currently active, the following command can be used in the Terminal application:
pmset -g | grep hibernatemode
In addition, users with administrator privileges can choose the hibernate mode. In order to do so, the following command can be used:
sudo pmset -a hibernatemode X
with X replaced by the value of the hibernate mode to set.