WEBVTT 00:00:00.000 --> 00:00:05.320 So your desktop computer probably has a big, chunky power supply and a thick, heavy cable 00:00:05.320 --> 00:00:08.320 running to the wall to provide all the power it needs. 00:00:08.320 --> 00:00:11.640 So have you ever wondered why the heck there's one of those little lithium-coin batteries 00:00:11.640 --> 00:00:15.280 sitting in your motherboard? Before we tell you, we'd like to thank Zach Bobroff 00:00:15.280 --> 00:00:18.760 of American Megatrends for collaborating with us on this video. 00:00:18.760 --> 00:00:22.040 Love you, Zach. So, the battery is there to power something 00:00:22.040 --> 00:00:27.440 called a CMOS chip. CMOS stands for Complementary Metal Oxide Semiconductor, 00:00:27.440 --> 00:00:31.320 and while that sounds complicated, all you really need to know is that it's a common way 00:00:31.320 --> 00:00:35.080 of manufacturing computer chips, used for applications from camera sensors 00:00:35.080 --> 00:00:41.280 to analog digital converters to amplifiers. But inside a PC, CMOS has historically been shorthand 00:00:41.280 --> 00:00:46.280 for the chip that contained your BIOS settings. The BIOS, or Basic Input Output System, 00:00:46.280 --> 00:00:51.400 is responsible for controlling low-level settings and initializing your hardware when your computer boots up. 00:00:51.400 --> 00:00:54.480 You're probably most familiar with it as that settings program you can access 00:00:54.480 --> 00:00:58.040 if you smash the delete or F1 key while your PC's booting up, 00:00:58.080 --> 00:01:02.240 getting some frustration out in the process. But the CMOS chip that keeps these settings 00:01:02.240 --> 00:01:06.680 was traditionally volatile memory, meaning all of these settings would be lost 00:01:06.680 --> 00:01:10.440 as soon as power was taken away. And since many people don't just leave their computers 00:01:10.440 --> 00:01:14.200 on 24-7, manufacturers put a coin battery on the motherboard 00:01:14.200 --> 00:01:18.280 to ensure the settings wouldn't just disappear if someone trips over the power cord, 00:01:18.280 --> 00:01:22.280 or does a magic spell. But fast forward to modern times, 00:01:22.280 --> 00:01:26.840 and it turns out that motherboard manufacturers don't use CMOS for BIOS settings anymore, 00:01:26.840 --> 00:01:31.200 partly because those old CMOS chips only held 128 bytes. 00:01:31.200 --> 00:01:34.920 But today's systems need to store lots more BIOS data. 00:01:34.920 --> 00:01:38.120 So instead, they just choose a chip with non-volatile RAM 00:01:38.120 --> 00:01:41.200 or NV RAM that not only has a higher capacity, 00:01:41.200 --> 00:01:45.040 but can store data persistently, even if there's no power going to the board. 00:01:45.040 --> 00:01:49.920 So what's the point of still having a battery then? Other than sentimental reasons, of course. 00:01:49.920 --> 00:01:55.040 So the reason there's still a CMOS battery is because there's still a CMOS chip. 00:01:55.040 --> 00:01:59.640 But instead of handling the BIOS, nowadays it's mostly just responsible for timekeeping. 00:01:59.640 --> 00:02:03.500 Just like a regular old wristwatch, your computer needs power of some sort 00:02:03.500 --> 00:02:07.520 if you wanna keep accurate time. So that battery ensures your computer's clock 00:02:07.520 --> 00:02:11.360 will tick away properly, even if you've left it unplugged for an extended period. 00:02:11.360 --> 00:02:15.980 And the fact that the lithium cell looks like the battery you'd put in your watch is just a nice bonus. 00:02:15.980 --> 00:02:19.320 But interestingly, many servers can keep time accurately 00:02:19.320 --> 00:02:24.800 without a CMOS battery, even if the power goes out. Instead of using a CMOS chip to keep time locally, 00:02:24.840 --> 00:02:28.480 servers often connect to an NTP server at boot time. 00:02:28.480 --> 00:02:32.820 NTP stands for Network Time Protocol, which is used to connect to a different server 00:02:32.820 --> 00:02:37.960 over the internet to fetch the time accurately. This isn't commonly used on home PCs though, 00:02:37.960 --> 00:02:42.260 so that little battery on your motherboard is still quite important. In fact, if you remove it, 00:02:42.260 --> 00:02:46.920 you'll probably find that your BIOS settings will still reset, just like they did in the old days. 00:02:46.920 --> 00:02:51.520 I'm assuming because of tradition. Just kidding, that was a joke, but actually not really. 00:02:51.520 --> 00:02:56.240 Because people were so used to removing the battery as a means of resetting the BIOS for so long, 00:02:56.240 --> 00:02:59.240 most PC manufacturers simply kept this functionality 00:02:59.240 --> 00:03:03.960 in place as an easy way to clear settings. Of course, there are a good number of motherboards out there 00:03:03.960 --> 00:03:08.320 that feature a clear CMOS button, either on the board itself or on the rear IO, 00:03:08.320 --> 00:03:13.040 that will also reset your BIOS settings, though its name is technically a misnomer now. 00:03:13.040 --> 00:03:17.560 The reason they kept the terminology was again, because folks have just been so used to using CMOS 00:03:17.560 --> 00:03:20.680 as a synonym for BIOS that the name just stuck. 00:03:20.680 --> 00:03:24.680 And although all this may be a little confusing, the good news is that the CMOS battery 00:03:24.680 --> 00:03:27.960 isn't something you have to worry about very often. They typically last for years 00:03:27.960 --> 00:03:32.360 before they might need to be replaced, but you might wanna have a copy of your BIOS settings 00:03:32.360 --> 00:03:38.960 saved somewhere anyways, especially if you're the type of person to spend hours getting your RAM timings just right. 00:03:38.960 --> 00:03:42.840 You can't get that time back, but you might as well have your BIOS settings. 00:03:42.840 --> 00:03:46.640 But I appreciate you spending the time that you can never get back to watch this video. 00:03:46.640 --> 00:03:50.200 Hey, like the video if you liked it, dislike it if you dislike it. Check out our other videos 00:03:50.200 --> 00:03:55.480 and comment below with video suggestions. Don't forget to subscribe and follow to Techquickie, 00:03:55.480 --> 00:03:58.040 which is this channel right here.