The motherboard battery or CMOS is one of the elements that we tend to go unnoticed in consumer electronics products, among which is our personal computer. We explain what this curious button battery is for and why it is so important for the proper functioning of many electronic devices that we use on a daily basis.
In this tutorial we are going to talk about the so-called motherboard stack or CMOS , and although many of you may be scared by the use of this complex signifier, in reality we are dealing with a relatively simple piece of hardware. Since it is nothing more than a battery or battery of a lifetime, but with a specific utility, in principle banal but totally necessary.
Button battery on the motherboard, what is it doing there?
When you see photos of a motherboard or simply when you open one, you will have noticed that there is a small button battery, due to its shape, in it, and at some point you will have wondered what it is for and what its functions are. In reality, there is nothing special about it and it is still the classic button cell of all life , but it is part of a scheme called “Non-volatile BIOS memory” and its operation is at least particular, due to the fact that the CMOS battery It is combined with a small RAM memory.
Today Flash memory or also called non-volatile RAM is quite common, but in its day this type of memory was extremely expensive and was only used in certain sectors. Therefore, in PCs, to store the BIOS data , a small SRAM memory was used, which has a problem, since it loses the contents of its interior once it is no longer powered. The solution? Add a small cell or battery that keeps it operational all the time. Thanks to this, it is possible to make changes to the BIOS parameters without them being lost after turning the computer on or off.
Although, as we have said before, motherboards can use flash memory. Using a CMOS battery makes sense since your SRAM write cycles are nearly infinite by comparison and you only need to change the battery every so often to keep it running. In contrast, if an NVRAM chip exceeds its write cycles, the entire board must be replaced.
ready to last
It is very difficult that during the expected life of a computer that a CMOS battery has a shorter life than its programmed obsolescence, however, over time they tend to give way and their acid is usually scattered on the plate . What makes extremely old systems require not only the maintenance of broken capacitors, but also the battery, and we may have the bad luck that the electronic circuit ends up deteriorating.
This is why finding vintage hardware in top working condition is so rare. In their day, these computers were designed so that their users in a period between 3 and 5 years would have replaced them with a better model due to the rapid progress of computing, with more capable and more powerful models continually coming onto the market.
The real time clock
When we talk about the clock signal of a processor we are talking about the milliseconds or nanoseconds that a pulse lasts today, with the frequency being its inverse and vice versa. However, if we have for example a 1 GHz processor, this will mean that each pulse will last 10 nanoseconds, but the concept of processor time in the form of seconds, minutes and hours to synchronize the calendar is important.
This is where real-time clocks and their relationship to the motherboard stack come in. These do nothing more than give us the date and time that we are operating at a frequency of only 32,768 Hz. Therefore, they have a frequency low enough to be powered by the CMOS battery and that the different applications know when we are in a universal language and measurement of time.
The failure of the CMOS battery can be seen as soon as the date of the computer suddenly returns to a very early date and both the system clock completely stalls after turning on the computer, which gives certain problems in the computer. applications and their operation depending on having the correct date, as well as the operating system.
Also found on other devices
Because this solution is a cheap way to store configuration information and keep it saved, we can also see it in other types of configuration-capable consumer electronics devices. Thus, your television remembers the tuning of the channels, the level of brightness, contrast and volume even after having turned it off thanks also to the use of a CMOS battery. Moreover, the most veterans will remember the games with saved games in the consoles prior to the use of memory cards, these did it through a CMOS battery. Today there are few games with these that have remained completely years after several decades of disuse.
Thus, we can see them in our video game consoles, the car radio, although their use is decreasing. Especially due to the fact that non-volatile memories have a much longer duration and due to the fact that their sudden breakage is not a problem for the manufacturer. Keep in mind that battery acid on top of an electronic circuit can render it useless and a shipment of faulty batteries on an electronic circuit can result in a lot of wasted money for the manufacturer that goes beyond the cost of a button cell battery.
DRM systems on consoles and their relationship with your motherboard stack
Both on PlayStation and Xbox, when we buy a game, what the server does is triangulate the following information:
- The information of our user account for the online system, which is controlled by the company’s servers, as well as our payment information.
- Information about our console, which includes the model, the SKU or serial number of the copy assigned to our console and the code number of the console.
Well, this information is stored in the small SRAM powered by the CMOS battery on the console’s motherboard. When we turn on a game, what the console does to verify that we have the permissions is to apply a secret mathematical formula, which only the manufacturer knows, but which uses the values stored in the CMOS stack. How can you guess if this is broken immediately we will no longer be able to play the games unless there is a continuous online check by the console. In other words, if one day the manufacturer shuts down its servers, it becomes totally impossible to recover the games once the battery content is gone.
