BIOS, CMOS, UEFI - What's the difference?

Summary

This video explains the BIOS, CMOS, and UEFI, detailing their roles in computer boot processes. BIOS is firmware on the motherboard that initializes hardware, performs a power-on self-test (POST), and finds boot devices. The CMOS chip retains custom BIOS settings using a battery. UEFI, a modern BIOS replacement, offers a user-friendly interface, supports larger storage drives, allows mouse use, and includes Secure Boot to prevent malicious software. The video also highlights the differences between BIOS and CMOS, addressing common confusion.

Takeaways

• 💻 BIOS stands for Basic Input/Output System and is the firmware on the motherboard that initializes the computer's hardware during booting.
• 🔍 The BIOS performs a Power-On Self-Test (POST) to ensure all hardware is functioning correctly before booting the operating system.
• 📢 Beep codes generated by the computer can indicate hardware issues, such as a keyboard error or a RAM module problem.
• 🔑 The BIOS software is stored on a non-volatile BIOS chip, which retains data even when the computer is powered off.
• ⏰ CMOS is a volatile chip that stores custom BIOS settings like date, time, and boot sequence, and requires a battery to maintain its settings.
• 🔋 The CMOS battery is a small button cell battery that, when removed and reattached, resets the BIOS to its factory default settings.
• 👉 The terms BIOS and CMOS are often confused; BIOS is the firmware, while CMOS is where the settings are stored.
• 🌐 UEFI, or Unified Extensible Firmware Interface, is a newer type of BIOS that offers a graphical user interface and supports larger storage drives.
• 🖱️ UEFI allows for mouse usage within its interface, unlike traditional BIOS which only supports keyboard navigation.
• 🔒 UEFI includes a secure boot feature that prevents unauthorized drivers from loading, enhancing system security against malware like rootkits.

Q & A

What does BIOS stand for?

BIOS stands for Basic Input/Output System. It is firmware built into the motherboard that initializes the computer's hardware during the boot process.

What is the purpose of BIOS during the computer startup?

The purpose of BIOS during startup is to perform a power-on self-test (POST), initialize the hardware, and search for a boot device to load the operating system.

What does the POST process involve?

The POST process involves testing the computer to ensure all hardware is functioning correctly and meeting the requirements before starting the operating system.

How does the computer indicate a successful POST test?

A successful POST test is indicated by a single short beep from the computer's internal speaker.

What does the absence of beeps or multiple beeps during POST suggest?

The absence of beeps or multiple beeps during POST suggests that the computer has failed the test and requires further troubleshooting.

What is a beep code and how is it useful?

A beep code is a series of beeps generated by the computer to help users identify specific hardware issues, such as a keyboard error or a problem with a RAM module.

Where is the BIOS software stored and how is it retained after power off?

The BIOS software is stored on a non-volatile BIOS chip on the motherboard, which retains its contents even after the power is turned off.

What is CMOS and how is it different from BIOS?

CMOS stands for Complementary Metal-Oxide-Semiconductor. It is a volatile chip that stores custom BIOS settings like date, time, and boot sequence. Unlike the BIOS chip, the CMOS chip requires constant power, typically supplied by a CMOS battery.

What is the function of the CMOS battery in a computer?

The CMOS battery provides constant power to the CMOS chip to maintain its settings, such as date, time, and boot sequence, when the computer is turned off.

What is UEFI and how does it differ from traditional BIOS?

UEFI stands for Unified Extensible Firmware Interface. It is a newer type of BIOS that offers a user-friendly graphical interface, supports larger storage drives, allows mouse usage, and includes a secure boot feature to prevent loading of unsigned drivers and malicious software.

Why is UEFI considered an improvement over traditional BIOS?

UEFI is considered an improvement because it provides a more user-friendly interface, better support for large storage drives, allows the use of a mouse, and includes security features like secure boot to protect against unauthorized software.

What happens if the CMOS battery is removed and reattached?

If the CMOS battery is removed and reattached, the BIOS resets to its default settings, erasing any custom configurations made by the user.

Outlines

00:00

💻 BIOS, CMOS, and UEFI Explained

This paragraph introduces the concepts of BIOS (Basic Input/Output System), CMOS (Complementary Metal-Oxide-Semiconductor), and UEFI (Unified Extensible Firmware Interface). BIOS is firmware on the motherboard that initializes computer hardware during boot-up and runs the power-on self-test (POST) to ensure all components are functioning correctly. If issues arise, the BIOS generates beep codes to help diagnose problems. The BIOS settings, such as date, time, and boot sequence, are stored in the CMOS chip, which is volatile and requires a battery to maintain its settings. The paragraph clarifies the difference between BIOS (the firmware) and CMOS (the chip storing user settings). It also introduces UEFI as a modern replacement for BIOS, offering a graphical interface, support for larger storage drives, and mouse usability within the interface.

05:02

🔒 UEFI's Secure Boot Feature

This paragraph focuses on a specific feature of UEFI called secure boot. Secure boot is designed to enhance the security of the boot process by preventing the loading of drivers that are not digitally signed, thus helping to protect against malware such as rootkits. It ensures that only trusted software can be executed during the boot process, adding an extra layer of security to the system.

Keywords

💡BIOS

BIOS stands for Basic Input/Output System. It is a type of firmware that is built into the motherboard and is responsible for initializing the computer's hardware during the boot process. The BIOS runs a power-on self-test (POST) to ensure all hardware components are functioning correctly before loading the operating system. In the video, BIOS is highlighted as the first step in the computer's startup sequence, emphasizing its foundational role in the computer's operation.

💡CMOS

CMOS stands for Complementary Metal-Oxide-Semiconductor. It refers to a special chip on the motherboard that stores certain settings such as the date, time, and boot sequence. Unlike the BIOS chip, the CMOS chip is volatile and requires a constant power source, typically provided by a small battery known as the CMOS battery. The video explains that if the CMOS battery is removed, the BIOS will reset to its factory default settings, erasing any custom configurations.

💡UEFI

UEFI stands for Unified Extensible Firmware Interface. It is a modern replacement for the traditional BIOS and comes with a graphical user interface, making it more user-friendly. UEFI can handle larger storage drives and supports the use of a mouse within its interface. It also includes a secure boot feature that prevents the loading of unsigned drivers and helps protect against malicious software. The video positions UEFI as an advancement over BIOS, offering improved functionality and security.

💡POST

POST stands for Power-On Self-Test. It is a diagnostic process that the BIOS runs when the computer is first turned on to ensure that all hardware components are functioning correctly. The video describes POST as a critical step in the boot process, where the computer checks its hardware before proceeding to load the operating system.

💡Boot Device

A boot device is a hardware component, such as an optical drive or a storage drive, from which the computer loads its operating system. The video explains that after initializing the hardware, the BIOS searches for a boot device to start the boot process, highlighting the importance of having a properly configured boot device for the computer to operate.

💡Beep Codes

Beep codes are a series of sounds made by the computer's internal speaker that indicate the results of the POST or other hardware issues. The video mentions that different beep patterns can signify various problems, such as a keyboard error or a RAM module issue, and that users can refer to the manufacturer's documentation to understand what each beep code means.

💡Non-volatile

Non-volatile refers to a type of memory that retains its data even when the power is turned off. The video explains that the BIOS software is stored on a non-volatile BIOS chip, ensuring that the firmware remains intact even after the computer is shut down.

💡Volatile

Volatile memory is a type of storage that requires a constant power source to maintain its data. The video describes the CMOS chip as volatile, meaning it needs power from the CMOS battery to retain settings like the date and time when the computer is off.

💡Southbridge

The southbridge is a part of a computer's chipset that manages input/output operations and is often where the CMOS chip is integrated. The video notes that on modern motherboards, the CMOS chip is not a separate entity but is part of the southbridge, which includes the real-time clock.

💡Secure Boot

Secure Boot is a feature of UEFI that prevents the loading of drivers that are not digitally signed, thus providing a layer of security against malicious software. The video highlights secure boot as an advantage of UEFI over traditional BIOS, emphasizing its role in protecting the system from unauthorized or potentially harmful software.

Highlights

BIOS stands for Basic Input/Output System and is firmware built into the motherboard.

BIOS initializes computer hardware during boot and searches for a boot device.

BIOS performs a power-on self-test (POST) to ensure hardware is functioning correctly.

A single beep indicates a successful POST, while no beeps or multiple beeps suggest hardware issues.

Beep codes help diagnose hardware problems, such as three long beeps for a keyboard error.

BIOS software is stored on a non-volatile BIOS chip on the motherboard.

CMOS chip stores custom BIOS settings like date, time, and boot sequence.

CMOS is volatile and requires a battery to maintain its settings when the computer is off.

The CMOS battery is a small button cell battery, typically located on the bottom right of the motherboard.

Removing and reattaching the CMOS battery resets BIOS to manufacturer default settings.

BIOS and CMOS are often confused, but BIOS is the firmware, while CMOS stores settings.

Modern motherboards integrate the CMOS with the real-time clock in the southbridge chipset.

UEFI (Unified Extensible Firmware Interface) is a newer type of BIOS with a graphical user interface.

UEFI supports larger storage drives and allows the use of a mouse within its interface.

UEFI includes a secure boot feature to prevent loading of unsigned drivers and malicious software.

Transcripts

What is the BIOS, CMOS, and UEFI? So that's what  we're going to talk about in this video. Now BIOS  

stands for basic input/output system. The BIOS  is firmware that's built into the motherboard  

that initializes the computer's hardware as  the computer is being booted. And then after  

it initializes the hardware, it then searches  for a boot device, such as an optical drive  

or a storage drive, to boot software such  as an operating system. So from the start,  

when you first turn on the computer, the computer  does what's called a power-on self-test or POST,  

which is run by the BIOS. It tests the computer to  make sure all the requirements are met and if the  

hardware is working correctly before starting the  operating system. If the computer passes the test,  

the internal speaker will make a short single  beep which indicates that the computer has passed  

the test and is booting up normally. However if  there are no beeps or multiple beeps then that  

means that the computer has failed the test and  something is wrong and the computer needs further  

troubleshooting to find out what the problem is.  So whether there are no beeps or multiple beeps,  

the computer will generate a beep code to help  you pinpoint the problem. So for example if the  

computer generates three long beeps, then  that could indicate a keyboard error. Or if  

the computer generates a continuous short beep,  then that could indicate a problem with a RAM  

module. So whatever BIOS is installed on the  computer's motherboard, you can always refer  

to the manufacturer's documentation to find  a list of beep codes and what they mean so  

you can pinpoint the problem and correct it. The  BIOS software is stored on the BIOS chip on the  

motherboard. The BIOS chip is non-volatile, which  means that the contents of a chip are retained  

even after the power is turned off. But even  after the computer is turned off, the computer  

does need to maintain certain settings, such as  the date and time, the boot sequence, and certain  

hardware settings. In other words, the custom  settings that you have configured in the BIOS.  

And these settings are stored on the motherboard  in a special chip called a CMOS chip. But unlike  

the BIOS chip which is non-volatile, the CMOS  chip is volatile. Meaning that it needs constant  

power to maintain its contents or settings. So in  order for the CMOS to maintain its settings while  

the computer is turned off, it uses a battery.  And this battery is called the CMOS battery. 

The CMOS battery is a small button cell  battery which can be seen on the surface  

of the motherboard and it's usually located on  the bottom right hand corner. And it's basically  

the same type of battery that is typically  used in wristwatches. Now as I stated before,  

the CMOS needs constant power that is supplied  by the battery. But if the battery is removed and  

then reattached, the BIOS will reset back to its  default settings from the manufacturer and erase  

any custom settings that you have configured.  Now a lot of people get confused about what's the  

difference between the BIOS and CMOS. And these  terms are often used to refer to the same thing,  

but they are different. So just to clarify  things, the BIOS is the actual firmware or  

program that comes with your motherboard. And  that firmware is stored in the BIOS chip. But  

the settings that you actually make to the BIOS,  such as a date and time, the boot sequence,  

fan speeds, and things like that, those  settings are retained in the CMOS chip.  

Now the CMOS chip is not necessarily  its own chip. On modern motherboards,  

it's been integrated with the real-time  clock that's part of the southbridge chipset.

Now a new type of BIOS is called UEFI. UEFI  stands for unified extensible firmware  

interface. Now most if not all new motherboards  are shipped with this newer type of BIOS. UEFI  

has several advantages over the old BIOS. And the first and most obvious, just by looking  

at it, is that it has a user-friendly graphical  user interface that supports different colors  

and even animations. Whereas the old BIOS has  your typical blue screen that resembles the  

windows blue screen of death. UEFI can also  recognize larger storage drives and you can  

even use a mouse in the UEFI interface,  whereas compared to the old BIOS, where  

mouse support wasn't even available and you  had to use your keyboard only. And UEFI also  

has a built-in feature called secure boot.  And secure boot stops any digitally unsigned  

drivers from loading and it also helps to  stop malicious software such as rootkits