▷ Clear cmos: what is it and how to do it step by step ??

As a PC user, it is very useful to know various maintenance routines to keep our equipment running smoothly. Many of our readers will be used to these tasks, but today we want to talk about one of the least known among the general public, and which is very useful. We are talking about clearing CMOS memory, or Clear CMOS. We tell you what a Clear CMOS consists of and how to do it.

Index of contents

Before we start, a couple of concepts

Before we begin, it is important to understand what we are dealing with within our team, especially if you aspire to use this method at some point. In this specific case, clearing CMOS (Clear CMOS) compromises two elements of our motherboard: CMOS memory and BIOS.

What is CMOS memory

CMOS memory (RAM-CMOS) is a type of memory in charge of storing information about the configuration of our system, specifically, the one used by the BIOS of our motherboard during the boot sequence of our computers.

The use of the term RAM for its definition is not arbitrary, it is a volatile memory that would lose the information inside if our equipment runs out of power, to avoid it, some type of battery (usually a button cell) is used to feed it.

Currently, many boards use EEPROM memories for this purpose. These are non-volatile and adequately fulfill the function of the old CMOS memories, but for cohesion in the text we will continue talking about CMOS memory.

What is the BIOS of our system

The second great protagonist of this text is the BIOS. Its name comes from the Basic Input-Output System and is the basic software for our motherboard. It is located on a dedicated chip inside our board and is responsible for the basic configuration and startup functions of our equipment. Through its options we can modify certain parameters of the behavior of the hardware connected to the motherboard.

BIOS chip. Image: Flickr, Uwe Hermann

The implications of clearing CMOS (Clear CMOS)

The Clear CMOS consists of emptying the information kept in the CMOS memory to force a reset of the BIOS configuration of our system, thus returning it to its factory settings.

The reason for using this action depends a lot on the malfunction of our equipment during startup. If we believe that the computer hardware does not suffer from physical problems (simply in poor condition), or presents compatibility problems that did not exist before, a complete reset of the BIOS through Clear CMOS may be a possible solution.

However, we must consider the implications of doing this for our team. Performing Clear CMOS will leave our BIOS in its factory state, so that both current configurations and installed updates will be removed.

For example, if we reset the BIOS of an X370 motherboard, we will not be able to use Ryzen 2000 or 3000 processors on our computer until we update the BIOS of our motherboard again.

How to perform Clear CMOS on our equipment

Being aware of all the previous information, if you want to perform this reset to the BIOS memory of your computer, there are usually three methods to carry out this task, although on more modern motherboards it may vary.

Perform the restart from the BIOS of our system

Unless we cannot access the BIOS window of our computer, this is the fastest and safest way to perform a Clear CMOS. To access the BIOS we must, during startup, press a specific key on our keyboard. This usually appears on the screen and is always indicated in the component manual.

Once inside, we navigate through the options to locate names such as Load factory default , or Clear BIOS settings . Once selected and completed we will have performed a reset of the system BIOS configuration. This method can also be completed on any current board.

• If you want to know more about how to access your BIOS, don't hesitate to take a look at our articles.

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Through the physical connection of our board

If it is not possible for us to access the BIOS of our system, we can attend to the physical means of our motherboard to perform the emptying of the BIOS memory. This step should always be performed with the equipment completely disconnected from the power, or it will not be performed properly.

On modern motherboards, the step is simple: locate the "Clear CMOS" switch on the motherboard and keep it active for a few minutes, easily identifiable through the component manual. However, if our motherboard is already old, the process varies.

If our board does not have such a switch, what we will have to locate is a series of pins on the board (two normally, although they may be more in some specific cases) and make contact with each other with a metal part for a few minutes. The pins in question should be able to be identified with some type of label, generally “CLR_CMOS” or “JBAT1”, although we can always identify them through the manual.

Removing the battery

As we mentioned earlier, CMOS memories are volatile and powered by a battery to keep your information intact. If we remove this battery and remove the current that supplies the equipment, the information in the memory will be erased with each power up until we replace the battery. This battery is associated with the internal clock of the equipment, and usually has about 8 years of life before needing to be replaced, although it can vary.

In the most modern motherboards this option does not exist, since it has non-volatile memories, although it is an option that can still be found in certain current ranges and on motherboards that are more than four years old.