Speaker 1: Welcome to Brainstuff from house Stuff Works dot com where
Speaker 1: smart happens. Hi am Marcia Brain with today's question, why
Speaker 1: does your computer need a battery? Most computers have a
Speaker 1: small battery about the size of a nickel. The battery
Speaker 1: is usually in some sort of holder that sits on
Speaker 1: the motherboard so it's easy to replace. Computers are not
Speaker 1: the only things that have a small battery like this.
Speaker 1: Camcorders and digital cameras often have them as well. Just
Speaker 1: about any gadget that keeps track of time. We'll have
Speaker 1: a little battery in your computer as well as these
Speaker 1: other gadgets. The battery powers a chip called the real
Speaker 1: time clock chip. The real time clock is essentially a
Speaker 1: courtz watch that runs all the time whether or not
Speaker 1: the computer has power. The battery powers this clock. When
Speaker 1: the computer boots up, part of the process is to
Speaker 1: query the real time clock chip to get the correct
Speaker 1: time and date. A little quartz clock like this might
Speaker 1: run for five to seven years off that small battery.
Speaker 1: Then it's time to replace the battery. In many cases,
Speaker 1: once the battery fails, your computer will no longer boot up.
Speaker 1: You would expect the computer to boot fine, but have
Speaker 1: an incorrect time and date. The reason your computer will
Speaker 1: not boot is because the real time clock chip also
Speaker 1: contains sixty four or more bytes of random access memory
Speaker 1: known as the se Moss RAM. The clock uses ten
Speaker 1: bytes of this space, leaving fifty four bytes for other purposes.
Speaker 1: The bios stores all sorts of information in the sims
Speaker 1: RAM area, like the number of drives, the hard disc
Speaker 1: drive type, and stuff like that. If the sms RAM
Speaker 1: loses power, the computer may not know anything about the
Speaker 1: hard disc configuration on your machine, and therefore it can't boot.
Speaker 1: More modern computers are not quite so dependent on the
Speaker 1: Sea Moss RAM. They store their settings in non volatile
Speaker 1: RAM that works without any power at all. If the
Speaker 1: battery goes dead, the clock fails, but the computer can
Speaker 1: still boot using the information in this non volatile RAM area. Then,
Speaker 1: once the computer can see the network, you can query
Speaker 1: a time server from the network and set the clock
Speaker 1: that way. Be sure to check out our new video podcast,
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