Why is there a BIOS battery on a computer board?

If you use a computer, you have probably encountered a situation where the computer notifies you that the time and date are set incorrectly in the settings. You set the time and date correctly, then turn off the computer and turn it on and the time is not set and is lost. One of the main reasons for this situation is that the BIOS battery, which is located on the motherboard, is dead. What is this battery for?

In the photo on the board you can see microcircuits, next to which there is the inscription BIOS. These microcircuits contain special programs BIOS - basic input - output system, which are launched together with the processor when the computer is turned on and check the state of the equipment and other functions. If everything is normal, control is transferred to the operating system. We can change some parameters of these programs if we go to the BIOS settings. Here in these settings we can change the time and date and other settings. The chips themselves where the BIOS programs are stored are non-volatile, they do not require power so that the programs are not erased, but the time settings that we set for them require power, because when we turn off the computer, the clock continues to run, and without power this is impossible. But the clock ticks not in the BIOS chips but in the south bridge chip, in my case this is the NH82801GB chip. Some of the many functions of this chip are volatile memory and a clock. And the fact that the clock ticks there you can understand by the quartz resonator at a frequency of 32.768 Hz, it is always located next to the south bridge

The photo shows a VT8235 microcircuit and next to it a battery and a quartz resonator. This microcircuit has a real-time clock, and the battery is used for it.

Here is a resonator in a black case

How to find out if the clock works when the computer is turned off? To do this, take the oscilloscope probe and connect it parallel to the quartz resonator, which is on the board and looks like a silver cylinder or in some other case. If the signal is poorly visible, connect the ground at the probe to the negative terminal of the BIOS battery.

A signal with a frequency of 32768 Hz will appear on the screen.This means that there is a signal and the clock is ticking, so when you turn on the computer, the clock continues to show the real time

But what happens if the battery runs out or is removed? Then the time and settings will be reset, and some programs on the computer can easily stop working or work incorrectly.To solve the problem with the BIOS settings, replace the battery on the motherboard in time