quote:

Turn off safe sleep [Useful for: does not properly go to sleep; fails
to wake from sleep]

"Safe Sleep" is a function writes the contents of RAM to a hard disk
buffer. The buffer is then accessed and restored to RAM, creating an
effect similar to merely putting the system to sleep though it has
actually been turned off (no power being used).

Mac OS X uses virtual memory data (RAM contents naturally stored on
disk as part of the virtual memory scheme) to formulate the sleepimage
file. When the system is put to sleep, Mac OS X culls from physical
RAM whatever data it cannot replicate from virtual memory and adds it
to the sleepimage file. As such, if the system is put to sleep
abruptly or something goes wrong during the write process, sleep can
fail to properly occur.

If you think safe sleep might be to blame for your regular sleep
issues, you can disable it by opening the Terminal (located in
Applications/Utilities) and entering the following command:

* sudo pmset -a hibernatemode 0

then pressing return.

You can then select "Go to Folder" under the "Go" menu in the Finder,
and enter: /private/var/vm then press return, and drag the file
sleepimage to the Trash..

In order to re-enable Safe Sleep, use the command:

* sudo pmset -a hibernatemode 3

in the Terminal.

Reset NVRAM [Useful for: does not properly go to sleep; wakes from
sleep while lid is closed; fails to wake from sleep]

A number of users report that resetting NVRAM resolves wake-from-sleep
issues. In order to perform this process, shut down your Mac, then
start it back up while immediately holding the following keys:
Command, Option, P and R. Hold the keys down until the computer
restarts and you hear the startup sound for the third time