What is the difference between hibernation and sleep modes?

What is the difference between “hibernation” and “sleep”? Both are power-saving states designed to achieve a compromise between fully-powered (”on”) and total shutdown. Without these low-power states (Stand By, Sleep, and Hibernate), you would have to go through the whole Windows’ boot process each morning. Although Vista has a shorter boot than previous versions, it still takes longer than most of us would like to wait — we are prone to desire ”instant gratification” these days — and so we use Stand By, Sleep, or Hibernate.

I wrote an article on power states and how to make adjustments to when they kick in, and use the Power Options control panel. To read (or review) this article, click this link, More reader questions answered: power states. Today I want to answer the title’s question, and tell you how to enable Hibernation as a power-saving option if it is not already a part of your Power Options control panel.

To begin with, Hibernation is a deeper “off state” than Sleep (or Stand By, as it’s sometimes called), and thus offers greater power savings at the cost of a longer rebooting time. It is considered a “safer” state, in terms of data. This is because, unlike Sleep mode, Hibernation not only shuts down the power to peripherals (monitor, etc.) and hard drives, but also turns off the power to the RAM memory chips.

When you remove the power to RAM, any data there is “lost”, forgotten, gone — whatever unsaved document, open window, and such as that.
Hibernation “writes” (Saves) all the 1’s and 0’s that are in RAM to a reference file (on your hard drive) before un-powering RAM, and it “reads” this file and reloads the data into RAM when you come out of Hibernation, thus restoring you to where you ended your last ’session’.
(This “reading” and loading is why it takes longer to “wake” than coming out of Sleep.)

Sleep/Stand By mode retains the power to your RAM. There is no saving of RAM contents to a file and there’s no need ‘load’ it — and thus it’s faster.. with less power savings. If there was a power interruption, for some reason, while in this state (and you don’t have a UPS), then your unsaved RAM contents would be gone.

Laptop computers typically come with the Hibernation power-settings option enabled and desktops don’t. If you would like to add the Hibernation option to your desktop, or if for some reason (such as a sneaky Windows Update) your Hibernation option has disappeared and you would like it back, here’s how to restore it: open a command prompt (Start >Programs >Accessories >Command Prompt) and type in “powercfg -h on” (no quotes) and hit Enter. That’s it. Now you will find Hibernation settings in the Power Options area of your Control Panel.

* If instead you would like to remove the Hibernation mode, and disable it from your automatic power-saving settings, the command is “powercfg -h off” (no quotes).

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* this post first appeared 11/7/07

Copyright 2007-9 © Tech Paul. All rights reserved. post to jaanix

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