Difference Between CMOS and BIOS

CMOS (Complementary Metal-Oxide Semiconductor) and BIOS (Basic Input/Output System) are two significant computer system components that serve different purposes.

CMOS is a form of technology used in the design of a computer's memory chip that saves crucial configuration data, whereas BIOS is the code that runs on a computer's motherboard and is in charge of initialising and testing hardware components during startup.

Read this article to find out more about CMOS and BIOS and how they are different from each other.

What is CMOS?

CMOS is an abbreviation for complementary metal-oxide semiconductor, which is the sort of technology used in the design of a computer's memory chip. The CMOS chip is a compact, low-power device that holds crucial computer system setup data, such as the current date and time, hard drive type, and memory installed.

The CMOS chip is typically found near the BIOS chip, which is in charge of initialising and testing hardware components during startup. The BIOS chip reads the configuration data saved in the CMOS chip during the startup process and uses it to configure the computer's hardware and software settings.

The CMOS chip is frequently used to store the current date and time. The operating system and other software applications use this information to precisely timestamp files and events. The hard drive type, amount of RAM installed, and boot sequence order are all examples of essential configuration data that may be saved in the CMOS chip.

What is BIOS?

BIOS stands for Basic Input/Output System. It is software that is built into a computer's motherboard and is responsible for initialising hardware components during boot-up and providing an interface between the operating system and the computer's hardware.

Aside from fundamental input/output operations, the BIOS also includes a collection of configuration options that allow the user to change various system parameters. These options include the boot sequence, the system date and time, and numerous hardware options such as memory speed and timing.

The BIOS has changed over time, and most modern computers use a newer firmware known as UEFI. UEFI is more advanced than the old BIOS in terms of boot and setting capabilities.

Difference between CMOS and BIOS

The following table highlights the major differences between CMOS and BIOS −








It is located on the motherboard as a low-power, non-volatile memory chip.

It is located on the motherboard in a ROM chip.

Power Consumption

CMOS consumes little power.

BIOS consumes high power.


It cannot be directly accessed.

It can be accessed through a setup utility.

Backup power

It requires backup power to maintain system configuration settings when the computer is turned off.

It doesn't require backup power.

Stands for

Complementary metal-oxide-semiconductor

Basic input/output system

Software Type

Memory technology

Type of firmware

Memory Type

Volatile Memory

Non-volatile Memory


In conclusion, CMOS and BIOS are two key components of a computer system that perform separate roles.

CMOS is in charge of storing important configuration data even when the computer is turned off, whereas BIOS is in charge of initializing and testing hardware components during startup and providing a basic set of input/output functions that allow the operating system to communicate with various hardware devices.

Understanding the difference between CMOS and BIOS is essential for troubleshooting and maintaining a computer system.

Updated on: 14-Apr-2023


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