So your desktop computer probably has a big, chunky power supply and a thick, heavy cable
running to the wall to provide all the power it needs.
So have you ever wondered why the heck there's one of those little lithium-coin batteries
sitting in your motherboard? Before we tell you, we'd like to thank Zach Bobroff
of American Megatrends for collaborating with us on this video.
Love you, Zach. So, the battery is there to power something
called a CMOS chip. CMOS stands for Complementary Metal Oxide Semiconductor,
and while that sounds complicated, all you really need to know is that it's a common way
of manufacturing computer chips, used for applications from camera sensors
to analog digital converters to amplifiers. But inside a PC, CMOS has historically been shorthand
for the chip that contained your BIOS settings. The BIOS, or Basic Input Output System,
is responsible for controlling low-level settings and initializing your hardware when your computer boots up.
You're probably most familiar with it as that settings program you can access
if you smash the delete or F1 key while your PC's booting up,
getting some frustration out in the process. But the CMOS chip that keeps these settings
was traditionally volatile memory, meaning all of these settings would be lost
as soon as power was taken away. And since many people don't just leave their computers
on 24-7, manufacturers put a coin battery on the motherboard
to ensure the settings wouldn't just disappear if someone trips over the power cord,
or does a magic spell. But fast forward to modern times,
and it turns out that motherboard manufacturers don't use CMOS for BIOS settings anymore,
partly because those old CMOS chips only held 128 bytes.
But today's systems need to store lots more BIOS data.
So instead, they just choose a chip with non-volatile RAM
or NV RAM that not only has a higher capacity,
but can store data persistently, even if there's no power going to the board.
So what's the point of still having a battery then? Other than sentimental reasons, of course.
So the reason there's still a CMOS battery is because there's still a CMOS chip.
But instead of handling the BIOS, nowadays it's mostly just responsible for timekeeping.
Just like a regular old wristwatch, your computer needs power of some sort
if you wanna keep accurate time. So that battery ensures your computer's clock
will tick away properly, even if you've left it unplugged for an extended period.
And the fact that the lithium cell looks like the battery you'd put in your watch is just a nice bonus.
But interestingly, many servers can keep time accurately
without a CMOS battery, even if the power goes out. Instead of using a CMOS chip to keep time locally,
servers often connect to an NTP server at boot time.
NTP stands for Network Time Protocol, which is used to connect to a different server
over the internet to fetch the time accurately. This isn't commonly used on home PCs though,
so that little battery on your motherboard is still quite important. In fact, if you remove it,
you'll probably find that your BIOS settings will still reset, just like they did in the old days.
I'm assuming because of tradition. Just kidding, that was a joke, but actually not really.
Because people were so used to removing the battery as a means of resetting the BIOS for so long,
most PC manufacturers simply kept this functionality
in place as an easy way to clear settings. Of course, there are a good number of motherboards out there
that feature a clear CMOS button, either on the board itself or on the rear IO,
that will also reset your BIOS settings, though its name is technically a misnomer now.
The reason they kept the terminology was again, because folks have just been so used to using CMOS
as a synonym for BIOS that the name just stuck.
And although all this may be a little confusing, the good news is that the CMOS battery
isn't something you have to worry about very often. They typically last for years
before they might need to be replaced, but you might wanna have a copy of your BIOS settings
saved somewhere anyways, especially if you're the type of person to spend hours getting your RAM timings just right.
You can't get that time back, but you might as well have your BIOS settings.
But I appreciate you spending the time that you can never get back to watch this video.
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