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UEFI (Unified Extensible Firmware Interface)

What is UEFI (Unified Extensible Firmware Interface)?

The UEFI, or Unified Extensible Firmware Interface, is a type of system firmware that provides an intermediary service between a computer's operating system and its hardware. UEFI is designed to replace the Basic Input/Output System (BIOS) firmware interface, offering benefits like enhanced startup times and improved support for larger hard drives.

What are some specific benefits of using UEFI over BIOS?

UEFI provides a number of advantages over BIOS. These include quicker boot times, the capacity to boot from larger than 2.2TB disks, better hardware and software compatibility, and improved security features such as Secure Boot which prevents certain types of malware attacks during system startup.


How does UEFI work?

UEFI oversees the post (Power-On Self Test) and the loading of the OS. When you switch on your computer, the UEFI firmware loads into the memory and performs a series of diagnostic tests on your hardware. Then, it identifies and initializes your hardware devices such as your hard drive, graphic card, among others, in a process known as the booting process. It finally passes control to the operating system.

What does the diagnostic test on the hardware entail, run by UEFI?

The diagnostic test run by UEFI, or Power-On Self Test (POST), checks the computer's system information and ensures that all hardware like RAM, processor, keyboard, and disk drives, is correctly installed and functional. If everything is in order, it proceeds with the boot process.


What is the booting process in UEFI?

The booting process in UEFI begins by performing POST to ensure all hardware is functional. It then initializes the hardware components and identifies the boot device. UEFI searches for and reads the bootloader from the selected boot device. This bootloader is then executed to load the operating system into memory.

What happens if there's a fault detected during POST?

If a fault is detected during the Power-On Self Test, the process will halt, and an error message will be displayed or beep codes will be sounded. Depending upon the nature of the fault, some corrective actions might be required like reseating the RAM or replacing a hardware component.


How are UEFI and an OS's bootloader linked?

UEFI and a bootloader have a direct relationship in the startup process of a computer. UEFI identifies and reads the bootloader from the boot device. The bootloader, in turn, is software that loads the operating system into the computer's memory from the hard disk. Thus, UEFI works in conjunction with the bootloader to start the operating system.

What happens if the bootloader is missing or corrupted?

If the bootloader is missing or corrupted, UEFI would not be able to load the operating system. This would halt the boot process and an error message would usually be displayed. In most cases, the resolution would be to repair or replace the bootloader using system recovery tools.


What does the UEFI interface look like?

A UEFI interface typically provides a much more user-friendly environment than traditional BIOS interfaces. It comes with a graphical user interface (GUI) which includes dropdown menus, radio buttons, checkboxes, and different screen layouts. Users navigate through the interface either by using a mouse or a keyboard.

How does one access the UEFI interface on a computer?

Generally, to access the UEFI interface, you would need to restart your computer and as it powers back on, press a specific key (commonly Esc, F2, F10 or Del) before the operating system begins to load. The particular key varies depending on the system manufacturer and model.


What is Secure Boot in UEFI and how it works?

Secure Boot is a security standard developed by members of the PC industry to help make sure that your PC boots using only software that is trusted by the PC manufacturer. When the PC starts, the firmware checks the signature of each piece of boot software, including firmware drivers (Option ROMs), EFI applications, and the operating system.

What happens if a piece of boot software fails the signature check carried out by the Secure Boot?

If a piece of boot software fails the signature check, Secure Boot prevents it from starting up. This means that only trusted components, preapproved by the OEM, are allowed to execute during the boot process, ensuring that no unsigned, modified or potentially harmful software can run.


How does UEFI manage device drivers?

Unlike BIOS, UEFI can manage device drivers on its own, without relying on the operating system. UEFI stores all the information about initializing and configuring devices in the firmware itself, allowing UEFI to control the hardware before the operating system loads.

What benefits does this ability to handle device drivers bring to the UEFI system?

By handling device drivers, UEFI can extend its compatibility to more types of hardware and allows the operating system to load much faster. In addition, this feature also makes it easier for hardware developers to create compatible, standardized drivers for many different operating systems.


What is a UEFI shell and what it is used for?

A UEFI shell is a command-line interface that provides a range of system control possibilities, including the ability to use scripts for automation. It can be used for various system maintenance tasks, such as loading UEFI drivers, running diagnostic tests, or manually loading and running operating systems.

How one can access the UEFI shell?

To access the UEFI shell, you would typically go through the UEFI interface. After booting into the interface, you would choose the option to launch the shell. The specifics can vary between different systems and motherboards.


How does UEFI firmware update process work?

Updating UEFI firmware varies by manufacturer, but it generally involves downloading an update from the manufacturer's website and either applying it within the operating system using a provided tool, or through the UEFI interface directly. After applying the update, a reboot is required for changes to take effect.

Can updating UEFI firmware pose any risks to the system?

Updating firmware poses a risk of component failure if done incorrectly. There's also the possibility of bricking the motherboard if power is lost during an update or if the wrong firmware version is applied. It is important to follow manufacturer instructions carefully during the process.


Can UEFI coexist with BIOS in a system, and why?

While UEFI is intended to replace BIOS, both can coexist in systems due to a feature known as Compatibility Support Module (CSM). This allows UEFI to emulate the BIOS interface for backward compatibility with older hardware or software that may not have been designed for UEFI.

What are the scenarios where keeping BIOS alongside UEFI might be useful?

Having BIOS alongside UEFI can be useful when using legacy operating systems or when running particular software or peripherals that don't support UEFI. Even so, as UEFI support expands and older systems are phased out, this is becoming less common.