What happens to a computer during a power outage?

After a power outage, why do computers retain information, whereas things like clocks reset themselves? Does it use a back up power source, like some calculators? If so, how long would this back up be able to prevent stored data loss?

4 Responses to “What happens to a computer during a power outage?”

  1. Ben  on November 28th, 2012

    Your computer’s hard drive uses magnets to store information. Your RAM (and the memory on your clock) need to constantly be refreshed, because they aren’t permanent but magnets don’t stop working because the power went out.

    Your computer does have a tiny battery that it uses to count the time when the computer is off or the power is out- those usually last about 5 years. You’ll be able to tell when that battery dies because every time your computer turns on, it will think it’s January 1st, 1970. then it will double check with the Internet and fix itself.


  2. Rajan Maharjan  on November 28th, 2012

    over load will occur during a power outage to the computer.


  3. Masked Musketeer  on November 28th, 2012

    Your computer’s motherboard has a battery that helps it keep the internal clock going. Sometimes you will notice that your computer’s timekeeping is off, when that happens that’s usually a sign that the battery inside the PC will need to be replaced because it’s going flat.
    The battery usually only needs replacing after about 4 years, by which time the desktop is pretty old and you might have moved onto a new desktop.

    Also, stuff that is already stored into your hard drive is safe.

    If you were working on a document for example, and haven’t saved it yet, the document does not yet exist as a file in the hard disk, but only as a temporary work stored on your RAM (Random access memory).

    RAM is volatile — meaning that the memory only works so long as it’s being fed power. If your computer loses power, the RAM stops working and it’s contents are flushed.
    So if any of your work has not been saved to the hard drive, you lose that progress.


  4. Pearls Before Swine  on November 28th, 2012

    Computers don’t retail *all* information when they lose power – anything that was in RAM (working) memory, like documents you were editing, is lost, because RAM memory requires power to be maintained. On the other hand, anything on the hard drive or flash memory is unaffected by power loss, because those forms of memory don’t require power to retain their contents.

    The only way to maintain all information on the computer when the power is lost is to use an uninterruptable power supply (UPS). It’s uses a battery that can power the computer for a short period (maybe 15 minutes) – long enough for the user to save any in-progress work and shut down the computer in an orderly manner.

    P.S. Most computers do have a small built in CMOS battery, but it’s only used to power the computer’s clock to keep track of the date and time and some low-level settings when the computer isn’t on. These batteries last for several years – usually the computer is obsolete long before the CMOS battery dies.


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