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UEFI(Unified Extensible Firmware Interface) and how is it different from BIOS

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The Unified Extensible Firmware Interface (UEFI), like BIOS (Basic Input Output System), is a firmware that runs when the computer is booted. It initializes the hardware and loads the operating system into the memory. However, being the more modern solution and overcoming various limitations of BIOS, UEFI is all set to replace the former. 

But what makes BIOS outdated? 

Present in all IBM PC-compatible personal computers, BIOS has been around since the late 1970s. Since then, it has incorporated some major improvements such as the addition of a user interface, and advanced power management functions, which allow BIOS to easily configure the PCs and create better power management plans. Yet, it hasn’t advanced as much as computer hardware and software technology since the 70s. 

Limitations of BIOS

  • BIOS can boot from drives of less than 2 TB. 3+ TB drives are now standard, and a system with a BIOS can’t boot from them. 
  • BIOS runs in 16-bit processor mode and has only 1 MB of space to execute. 
  • It can’t initialize multiple hardware devices at once, thus leading to a slow booting process.
  • BIOS is limited in its configuration options and can be difficult to use for advanced users. 
  • BIOS is vulnerable to malware attacks, such as rootkits, that can exploit vulnerabilities in the firmware.

UEFI, or Unified Extensible Firmware Interface, is a type of firmware interface used in modern computers to replace the traditional BIOS (Basic Input/Output System). UEFI provides a more advanced and flexible interface than BIOS, allowing for improved boot times, more efficient power management, and support for larger hard drives and partitions.

One of the main differences between UEFI and BIOS is the way they handle system initialization. With BIOS, the firmware is stored in a read-only memory (ROM) chip on the motherboard, and the firmware is responsible for loading the operating system from the hard drive. In contrast, UEFI is stored in non-volatile memory on the motherboard and is capable of directly loading the operating system from the hard drive.

UEFI also provides more advanced features than BIOS, such as secure boot, which helps prevent malicious software from loading during the boot process. UEFI also supports graphical interfaces and provides more detailed system information and configuration options than BIOS.

Difference between the Booting Process with UEFI and the Booting Process with BIOS

  • Booting Process With BIOS : When BIOS begins its execution, it first goes for the Power-On Self Test (POST), which ensures that the hardware devices are functioning correctly. After that, it checks for the Master Boot Record in the first sector of the selected boot device. From the MBR, the location of the Boot-Loader is retrieved, which, after being loaded by BIOS into the computer’s RAM, loads the operating system into the main memory. 
  • Booting Process With UEFI : Unlike BIOS, UEFI doesn’t look for the MBR in the first sector of the Boot Device. It maintains a list of valid boot volumes called EFI System Partitions. During the POST procedure, the UEFI firmware scans all of the bootable storage devices that are connected to the system for a valid GUID Partition Table (GPT), which is an improvement over MBR. Unlike the MBR, GPT doesn’t contain a Boot-Loader. The firmware itself scans the GPT to find an EFI System Partition to boot from, and directly loads the OS from the right partition. If it fails to find one, it goes back to the BIOS-type Booting process called ‘Legacy Boot’. 

Advantages of UEFI over BIOS

  • Breaking Out Of Size Limitations : The UEFI firmware can boot from drives of 2.2 TB or larger with the theoretical upper limit being 9.4 zettabytes, which is roughly 3 times the size of the total information present on the Internet. This is due to the fact that GPT uses 64-bit entries in its table, thereby dramatically expanding the possible boot-device size. 
  • Speed and performance : UEFI can run in 32-bit or 64-bit mode and has more addressable address space than BIOS, which means your boot process is faster. 
  • More User-Friendly Interface : Since UEFI can run in 32-bit and 64-bit mode, it provides a better UI configuration that has better graphics and also supports mouse cursor. 
  • Security: UEFI also provides the feature of Secure Boot. It allows only authentic drivers and services to load at boot time, to make sure that no malware can be loaded at computer startup. It also requires drivers and the Kernel to have a digital signature, which makes it an effective tool in countering piracy and boot-sector malware.
  • Uses GPT instead of MBR: As mentioned earlier, UEFI firmware scans all of the bootable storage devices connected to the system for a valid GUID Partition Table (GPT), which is an improvement over the Master Boot Record (MBR) used by BIOS. GPT is more advanced and can support larger drives and partitions, as well as more partitions per drive.
  • Handle multiple operating systems: With UEFI, it’s possible to have multiple operating systems installed on a single hard drive or SSD, and the firmware can manage them all. This is because UEFI maintains a boot manager that can choose which operating system to load at startup.
  • More detailed system information: UEFI can provide more detailed information about the system hardware and firmware configuration, including information about the CPU, memory, storage devices, and firmware settings. This information can be useful for troubleshooting and diagnostics.
  • Supports network booting: UEFI firmware can support network booting, which means that the operating system can be loaded from a server on the network rather than from local storage. This can be useful for remote management and deployment of operating systems.
  • Supports more modern technologies: UEFI supports newer technologies such as USB 3.0, NVMe, and PCIe, which can improve performance and functionality compared to BIOS.

UEFI doesn’t require a Boot-Loader, and can also operate alongside BIOS, supporting legacy boot, which in turn, makes it compatible with older operating systems. Intel plans to completely replace BIOS with UEFI, for all its chipsets, by 2020.


Last Updated : 22 Apr, 2023
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