Unlike Windows, Mac OS doesn’t offer a hibernate or deep sleep mode – selecting Sleep from the Apple menu just puts a Mac into a low-power state (suspend to RAM) that, while quick to resume, still keeps the contents of memory in memory.
This isn’t much of a problem on a desktop Mac that’s plugged into the mains, but it is a problem for MacBooks that are being used on battery power.
A MacBook in sleep mode still draws power, which means if you close the lid (the standard way to trigger sleep mode on a MacBook) and put an unplugged MacBook aside for a few days, you may come back to a flat battery.
As it turns out, more recent MacBooks do actually enter a hybrid sleep mode when you close the lid. Apple calls it Safe Sleep (much like that used in Windows Vista) and the contents of memory are written to disk before the MacBook enters its low-power sleep state. This is an insurance policy for those times when leave a MacBook in sleep mode away from the mains until the battery runs flat. When you power on, the MacBook will still resume to where you left it, but it will take a little longer as it’s restoring data from disk rather than RAM.
So, if Mac OS already has a hibernate mode, why can’t it be activated manually? Well, it can… (more…)