Differences Between UEFI and BIOS, and Which One You Should Use?

Uefi Or Legacy Bios Computer Laptop Reboot Home

UEFI vs. BIOS, which one is better and which one you should use? It’s a good question for anyone who wants to find out how the underlying hardware works so they can personalizing the nuts and bolts of their personal computers. In short, UEFI is newer, better and comes loaded on most modern PC. But things are not as simple as black and white. Here’s a rundown of the functionalities both UEFI and BIOS provide and why you might choose one over the other.

The basics

BIOS and UEFI are two firmware interfaces for computers which work as an interpreter between the operating system and the computer firmware. Both of these interfaces are used at the startup of the computer to initialize the hardware components and start the operating system which is stored on the hard drive.

Uefi Or Legacy Bios Boot

BIOS (Basic Input Output System) works by reading the first sector of the hard drive which has the next device’s address to initialize or code to execute. BIOS also selects the boot device that needs to be initialized for starting the operating system. Since BIOS has been in use since the very beginning (it exists since the MS-DOS era), it still works in 16-bit mode, limiting the amount of code that can be read and executed from the firmware ROM.

UEFI (Unified Extensible Firmware Interface) does the same task a little differently. It stores all the information about initialization and startup in an .efi file instead of the firmware. This file is stored on the hard drive inside a special partition called EFI System Partition (ESP). The ESP partition also contains the boot loader programs for the Operating System installed on the computer.

UEFI is meant to completely replace BIOS and bring in many new features and enhancements that can’t be implemented through BIOS. Some of those features are discussed below.

Breaking out of size limitations

BIOS uses the Master Boot Record (MBR) to save information about the hard drive data while UEFI uses the GUID partition table (GPT). The major difference between the two is that MBR uses 32-bit entries in its table which limits the total physical partitions to only 4. Each partition can only be a maximum of 2TB in size, while GPT uses 64-bit entries in its table which dramatically extends the support for size possibilities of the hard drive. (More on difference between MBR and GPT).

In addition, UEFI supports larger HDDs and SDDs. UEFI’s theoretical size limit for bootable drives is more than nine zettabytes, while BIOS can only boot from drives 2.2 terabytes or smaller.

Speed and performance

Since UEFI is platform independent, it may be able to enhance the boot time and speed of the computer. This is especially the case when you have large hard drives installed in your computer. This enhancement depends upon how UEFI is configured to run. UEFI can perform better while initializing the hardware devices. Normally this speed enhancement is a fraction of the total boot time, so you will not see a huge difference in overall boot time. Developers can make use of UEFI shell environment which can execute command from other UEFI apps optimizing the performance of the system further.



Secure boot is a feature of UEFI that has been implemented in Windows 8 and is now the standard for Windows 10. The biggest benefit of UEFI is its security over BIOS. UEFI can allow only authentic drivers and services to load at boot time, making sure that no malware can be loaded at computer startup. Microsoft implemented this feature to counter piracy issues in Windows, while Mac has been using UEFI for quite some time now. Secure Boot works by requiring a digital signature of boot loaders which should require digital signature by the Kernel. This process continues until the operating system is completely started. This secure boot feature is also one of the reason why it is more difficult to install another operating system on a Windows machine.

Why Choose UEFI?

One reason to choose this over the more familiar BIOS is that Intel no longer intends to support the “traditional” BIOS in 2020.


UEFI provides the following functionality and advantages:

  • Languages: BIOS is written in assembler, while UEFI is written in simpler C-language.
  • Drives: UEFI supports larger HDDs and SDDs. UEFI’s theoretical size limit for bootable drives is more than nine zettabytes, while BIOS can only boot from drives 2.2 terabytes or smaller.
  • Drivers: UEFI has intricate yet discrete drivers, while BIOS uses drivers in option ROM (read-only memory). With BIOS, updating the hardware requires re-tuning the ROMs for compatibility. This specification applies to separately-written, upgradeable UEFI drivers.
  • Boot time: In most cases, UEFI provides a faster booting time for the operating system.
  • Security: UEFI offers improved security features. “Secure Boot” prevents the computer from booting from unsigned or unauthorized applications. The OS must contain a recognizable key. Without Secure Boot enabled, a PC is vulnerable to malware corrupting the startup process.
  • Data processors: UEFI runs in 32-bit or 64-bit mode. BIOS runs only in 16-bit mode and may utilize only 1 MD of executable memory.
  • GUI: UEFI provides a more intuitive graphical user interface that you may navigate with a mouse and keyboard, unlike BIOS.

Another advantage of UEFI is that an industry-wide interface forum maintains it and it is more manufacturer-agnostic than BIOS.

Why Choose BIOS?

Some reasons why a user might choose Legacy BIOS instead of UEFI include:

  • BIOS is ideal if you don’t require fine control over how your computer operates.
  • BIOS is also sufficient if you only have small drives or partitions. Although many newer hard drives exceed BIOS’ 2-terabyte limit, not every user requires that amount of space.
  • UEFI’s “Secure Boot” feature may result in OEM manufacturers preventing users from installing other operating systems on their hardware. If you stick with BIOS, you side-step this issue.
  • BIOS provides access to hardware information in the interface, while not every implementation of UEFI does so. Hardware specs are accessible within the OS, however.

Some newer PCs allow you to run UEFI in Legacy BIOS Mode. Users who wish to maintain machines running older operating systems, including Windows 7, will want to enable this feature.

Uefi Or Legacy Bios System Information

When a Background Update Is a Big Deal

Most modern PCs come with UEFI. This will provide you with the latest security safeguards, an easier-to-use interface for tweaking your machine and support for modern operating systems and beefier specs. While there are some reasons to stick with Legacy BIOS or use its compatibility mode, most people will welcome the upgrade to UEFI, or never know it happened.

Image credit: Boot Mode UEFI/BIOS


  1. Perhaps a good idea for another article would be an explanation of how to install an alternative OS on a computer with UEFI’s “Secure Boot” feature enabled.

  2. re something like an ide or sata interface. it is the same for everyone, the terminology is the same for everyone making or using that particular interface. in the case of uefi the industry has not quite come together on terminology and/or function. if the same terms are used by different motherboard or computer manufacturers the function is more often very different and the same is true for the other way around. i’m sorry to disagree but THIS IS NO STANDARD.

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