In this tutorial, we are going to talk about calling motherboard or CMOS battery, and although many of you may be frightened by the use of this complex signifier, in reality we are dealing with a piece of hardware with a relatively simple operation. Since it is neither more nor less than a battery or a battery for life, but with a specific utility, in principle banal but totally necessary.
Button cell on the motherboard, what’s it doing there?
When you see pictures of a motherboard or just when you open one, you will have noticed that there is a small button battery, by its shape, in it, and at some point you will have wondered what it serves and what its functions are. There’s really nothing special about it it’s still the classic button battery of a lifetimebut it is part of a scheme called “Non-volatile BIOS memory” and its operation is, to say the least, particular, owing to the fact that the CMOS battery is associated 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 industries. So on PC to store BIOS data a small SRAM memory was used, which is a problem, since it loses the contents of its interior once it loses power. 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 settings without them being lost after turning on or off the computer.
Although, as we said before, motherboards can use flash memory. Using a CMOS battery makes sense because your SRAM write cycles are almost infinite in comparison and you only have to change the battery once in a while to keep it going. On the other hand, 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 should have a life shorter than its planned obsolescence, however, over time they tend to fail and their acid generally disperses on the plaque. What makes systems extremely old requires not only the maintenance of broken capacitors, but also the battery, and one can be unlucky that the electronic circuit ends up deteriorating.
That’s why it’s so rare to find vintage gear in perfect working order. In their time, these computers were designed so that their users in a period of between 3 and 5 years would replace them with a better model due to the rapid advances in computing, with better and more powerful models continuously arriving on 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 today lasts, the frequency being its inverse and vice versa. However, if we have for example a 1 GHz processor, it will mean that each pulse will last 10 nanoseconds, but the notion 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 battery 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 low enough frequency to be powered by the CMOS battery and that the different applications know when we are in a universal Language and measurement of time.
CMOS battery failure can be seen as soon as the computer date suddenly reverts to a very early date and the system clock completely stalls after the computer is turned on, causing some problems in applications and their operation depending on having the correct date, as well as the operating system.
Also available on other devices
Since this solution is an inexpensive way to store configuration information and persist it, we can also see it in other types of configuration-capable consumer electronics devices. Thus, your TV remembers the tuning of the channels, the level of brightness, contrast and volume even after turning it off thanks also to the use of a CMOS battery. In addition, the most veterans will remember the games with games saved in consoles before the use of memory cards, these did so via a CMOS battery. Today there are few games with these that have remained completely for years after several decades of disuse.
Thus, we can see them in our video game consoles, the car radio, although their use is decreasing. In particular due to the fact that non-volatile memories have a much longer duration and due to the fact that their sudden rupture is not a problem for the manufacturer. Keep in mind that battery acid on top of an electronic circuit can render it useless and sending defective batteries to an electronic circuit can result in a lot of wasted money for the manufacturer that goes beyond the cost of a button cell.
DRM systems on consoles and their relationship to your motherboard battery
Both on PlayStation and Xbox, when we buy a game, what the server does is triangulate the following information:
- Our user account information for the online system, which is controlled by Company servers, and our payment information.
- Information about our console, which includes the model, SKU or serial number of the copy assigned to our console and the code number of the console.
Well, that information is stored in the small CMOS battery-powered SRAM 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 won’t be able to play the games anymore unless there is a continuous online check by the console. In other words, if one day the manufacturer stops its servers, it becomes totally impossible to recover the games once the contents of the battery have been exhausted.