BIOS vs UEFI: What is the difference, and which one is better

While powering on your computer might look as simple as pressing a single button, that is really not the case. Behind the scenes, a complex process is at work. Something has to wake up the hardware, run basic checks, and hand things over to your operating system. 

For decades, this job was handled by the BIOS, a firmware standard dating back to the early 1980s. But as computers became faster and more complex, the old BIOS struggled to keep up, giving rise to UEFI. 

UEFI came in, bringing modern features like quicker boot times, better security, and support for larger drives.

Both BIOS and UEFI aim to do the same job, which is to boot your system, but the way doit is very different.

In this article, we will look at what BIOS and UEFI are, highlight their differences, clear up common misconceptions, and help you figure out which one is better for today’s machines.

What is the boot process?

The boot process refers to a bunch of steps your computer follows when it is powered on to initialize hardware, test components, load the operating system, and make the system ready for use. 

When you press the power button, the CPU begins execution at a predefined reset vector, which is mapped to the system firmware (UEFI/ BIOS) stored in non-volatile memory. After this, the process looks something like this:

1. The firmware runs POST, a diagnostic check, to ensure all critical hardware components like CPU, memory, storage drives, and input/output devices are working properly. And if any issues are found, they are usually signaled with beeps or error codes, and the boot process is paused. 

2. When the POST is successful, the firmware initializes the peripheral devices, so they are ready to function as needed. 

3. Next, the firmware code looks at the configured boot order to find a storage device that contains a valid bootloader. The primary job of this bootloader is to find the operating system.

4. Once the boot device is identified, the firmware reads the first sector, which contains the bootloader program.

5. Once the bootloader is located, the firmware loads it into memory and hands over control of the system to it. The bootloader, which provides a more advanced environment, loads the OS kernel into the memory and then transfers control to it.

6. The OS then takes over to finish the boot process. It will initialize system components and file systems, load drivers, and prepare the user interface or login screen so the user can begin working. 

What is Legacy BIOS?

The legacy BIOS is the original firmware interface that acts as a fundamental link between your computer's hardware and its operating system. It initializes the hardware and starts the above-mentioned boot process. 

BIOS has been historically stored in a small ROM chip on the motherboard, which later changed to EPROM, EEPROM, and flash memory, supporting easier updates and bug fixes.

Despite its importance in early computing, BIOS comes with several limitations. For example, it can only handle boot disks up to 2.2 TB because it relies on the older MBR partitioning scheme. Plus, its setup screen is text-based, navigated with the keyboard, and offers only a handful of configuration options. 

As the name clearly suggests, legacy BIOS also lacks many of the advanced features we now expect, such as Secure Boot and a graphical user interface (GUI), which are available in modern UEFI firmware.

What is UEFI?

UEFI is the modern firmware interface that replaces the older legacy BIOS firmware. Like BIOS, UEFI is also responsible for initializing hardware during startup and handing control over to the operating system, but it brings many advancements and improvements over legacy BIOS. But first, let us dig into its origin story. 

UEFI traces back its origin to Intel's efforts to address the limitations of the traditional BIOS architecture in the late 1990s. By then, personal computers had evolved far beyond the simple systems for which the BIOS was designed. BIOS's 16-bit architecture, reliance on the MBR, and slow, sequential boot process were creating some serious difficulties.

To tackle these challenges head-on, Intel created the Extensible Firmware Interface (EFI) as part of its development for the Itanium processor family. The goal was to build a modern, scalable, and flexible firmware interface that could:

• Handle 64-bit systems.

• Support large storage devices.

• Allow for a parallelized, faster boot process.

• Provide a standardized environment for hardware vendors to write drivers.

While EFI was no doubt a major step forward, Intel's exclusive control over the standard was not really helping the broader industry. To encourage wider adoption, Intel handed over the development of EFI to a non-profit organization called the UEFI Forum in 2005.

And with this transfer, the Unified Extensible Firmware Interface (UEFI) came into existence. The UEFI Forum, which includes major technology companies like Microsoft, Apple, AMD, and various hardware manufacturers, standardized the specification. This collaboration made sure that UEFI would be an industry-wide solution that could replace legacy BIOS and become the modern standard for personal computing.

At its core, this modernization comes from a major design change. Unlike BIOS, which relies on the MBR in the first sector of a disk, UEFI uses the EFI System Partition (ESP), a dedicated disk partition containing .efi executables, including bootloaders. 

It stores all data about initialization and startup in an .efi file, which is located on a specific partition called the EFI System Partition (ESP) on the hard disk. This ESP partition also contains the bootloader. 

UEFI also comes with a CSM, or Compatibility Support Module, that enables it to mimic a traditional BIOS environment. Its primary purpose is to provide backward compatibility, allowing modern computers with UEFI to boot from older operating systems and hardware (such as hard drives with an MBR partition) that were designed for BIOS. However, Intel-based computers do not support CSM. 

Legacy BIOS vs UEFI: Differences between the two

Function-wise, both BIOS and UEFI are almost similar. Where they differ the most is in the notable improvements that UEFI provides in terms of hardware, compatibility, and performance. Let us examine the differences between UEFI and BIOS one by one. 

Architecture and speed

Legacy BIOS operates in a 16-bit environment, which limits its performance and capability. The boot process is also slow and sequential, as it must check hardware components one at a time. 

UEFI, on the other hand, runs in a 32-bit or 64-bit environment. This allows it to perform parallel initialization of hardware, which results in significantly faster boot times and more efficient operation.

Storage and partitions

BIOS utilizes the Master Boot Record (MBR) partitioning scheme. The MBR has a major limitation: it can only support hard drives up to 2 terabytes in size. 

UEFI utilizes the GUID Partition Table (GPT). GPT removes the 2-terabyte limit, allowing support for modern, high-capacity hard drives and solid-state drives.

Security

BIOS lacks any built-in security features, leaving the boot process vulnerable to sophisticated malware like rootkits and bootkits. UEFI, on the other hand, includes a critical security feature called Secure Boot. 

When enabled, Secure Boot verifies that all drivers and bootloaders are digitally signed by a trusted source, effectively blocking malicious code from hijacking the startup process.

Interface and usability

The BIOS setup interface is a simple, text-based menu that can only be navigated using a keyboard. It is functional but basic. The UEFI interface is a modern graphical user interface (GUI) that supports a mouse. This makes it far more user-friendly and easier to configure system settings.

Extensibility and network support

BIOS is a static, non-extensible firmware. Its code is simple and difficult to update. UEFI is designed to be highly extensible. It can use its own drivers and even has built-in network support, which allows for remote diagnostics, firmware updates over the internet, and network booting, making it a much more flexible and powerful solution for both users and IT administrators.

This comparison table further clarifies the differences between BIOS and UEFI.

BIOS vs UEFI: Which one is better?

All things considered, coming to the final verdict is not all that hard. It is evidently clear that UEFI, with its advanced functionalities, does present a better alternative to BIOS. That said, there are still situations where BIOS and UEFI behave differently. To give you a clearer picture, we have outlined some UEFI vs. BIOS scenarios and use cases below. 

1. For modern systems, gaming, and hosting servers

UEFI is clearly the better choice. It offers faster boot times, better security, support for large drives and many partitions, a user-friendly interface, and flexibility for modern hardware and software environments.

2. For older or legacy systems

BIOS may still be used in systems with very old hardware or software that does not support UEFI booting or low-power devices designed with basic hardware specifications.

3. Security considerations

UEFI provides solid defense against bootkits and rootkits with Secure Boot, which BIOS cannot offer. This makes UEFI much safer in the face of evolving cybersecurity threats.

4. Performance and usability

UEFI is designed to support faster booting through parallel hardware initialization, but actual boot speed depends on the specific firmware implementation and system configuration. It also provides a graphical setup interface, making system configuration easier than BIOS’s text-only menus.

5. Scalability and compatibility

UEFI evolves with new technologies. Its flexible framework ensures ongoing compatibility with future hardware and software innovations, making it the smarter option for systems that need to stay current.

BIOS, on the other hand, has reached its technological limits. Its architecture struggles to support emerging hardware standards and modern software requirements, making it less viable for long-term use. 

Additional read: Cybersecurity tips for MSPs

How to check if your system uses BIOS or UEFI?

You can easily check if your system uses BIOS or UEFI with the help of these methods:

1. Using System Information

• Press Win + R to open the Run dialog box. And then type “msinfo32,” and press Enter to open System Information.

• Look for the field BIOS Mode.

• If it says “Legacy,” your system uses BIOS.

• If it says “UEFI,” your system uses UEFI.

2. Using Command Prompt

• Open Command Prompt as Administrator.

• Run the command “bcdedit.”

• In the output, look for the Windows Boot Loader section and find the path.

• If the path ends with winload.exe, it is BIOS.

• If it ends with winload.efi, it is UEFI.

3. Checking directory on LINUX systems

• If you use LINUX, run the following command: “[ -d /sys/firmware/efi ] && echo "UEFI Boot Detected" || echo "Legacy BIOS Boot Detected"” on the terminal. 

• If the directory “/sys/firmware/efi” exists and the command returns "UEFI Boot Detected," your system is currently running in UEFI mode.

• If it returns "Legacy BIOS Boot Detected," your system is running in Legacy BIOS mode.

How to switch from BIOS to UEFI?

Switching from BIOS to UEFI involves several steps. Plus, there is a condition that your computer's hardware should support UEFI. The process often involves reconfiguring your hard drive and reinstalling your operating system. Here is how you can make the switch:

1. Verify if your system currently uses Legacy BIOS or UEFI. 

-Use the System Information method or check it through the CMD. 

2. Check your disk partition style.

-Open Disk Management by pressing Win + X.

-Right-click your system drive, usually C, and then follow this sequence: Properties > Volumes tab > check Partition Style.

-If it shows MBR, you need to convert it to GPT.

3. To convert MBR to GPT, use the “mbr2gpt” command.

-Open Command Prompt as Administrator.

- Type the “mbr2gpt /convert /allowFullOS” command. 

4. Change firmware settings to UEFI.

-Restart your PC and enter BIOS setup by pressing the relevant key during boot.

-Find the Boot or Boot Mode setting.

-Change from Legacy BIOS or CSM (Compatibility Support Module) to UEFI mode.

-Save changes and exit BIOS.

5. Restart your system and confirm from System Information that the BIOS Mode now shows UEFI.

<Highlight when publishing>

Always back up important files to an external drive or cloud storage while switching to UEFI because disk operations can risk data loss.

Troubleshooting boot issues after switching to UEFI

While shifting to the UEFI, you may encounter some of the boot issues, which you can troubleshoot in the following ways:

Check UEFI Firmware Settings

• Restart your PC and enter the UEFI setup (usually by pressing keys like F2, Del, or Esc during boot).

• Verify Secure Boot is enabled or disabled as required by your OS. Sometimes disabling Secure Boot temporarily helps troubleshoot boot issues.

• Ensure the boot mode is UEFI and not Legacy/CSM.

Repair the EFI bootloader

1. Boot into the recovery environment. 

• Use a Windows installation USB or DVD to boot the PC.

• Select "Repair your computer" instead of installing.

• Navigate to Troubleshoot > Advanced Options > Command Prompt.

2. Identify and assign EFI partitions.

• In Command Prompt, run the command:

“diskpart

select disk 0

list vol”

• Locate the EFI partition (usually FAT32, around 100-600MB).

• Assign a drive letter to it (e.g., R:), run the following command:

“select vol <EFI_volume_number>

assign letter=R:

exit”

3. Repair EFI bootloader.

• Navigate to the EFI boot folder on the assigned drive by using the following command:

“cd /d R:\EFI\Microsoft\Boot\”

• Fix the boot record and rebuild the BCD store using the command:

“bootrec /FixBoot

ren BCD BCD.bak

bcdboot C:\Windows /l en-us /s R: /f ALL

bootrec /RebuildBcd”

4. Restart and test

• Remove the USB/DVD and restart the PC.

• It should boot normally if the EFI bootloader was repaired successfully.

Additional read: Building a rock-solid MSP tech stack

Common misconceptions about BIOS vs UEFI

There are several misconceptions floating around the industry when it comes to UEFI vs BIOS. Here, we clarify most of these misconceptions.

1. BIOS is for old systems only, UEFI is for new systems only.

Reality: BIOS is a legacy firmware and no longer used on new motherboards. However, many UEFI implementations include Compatibility Support Module (CSM) that emulates BIOS to support older operating systems and hardware.

2. You can "upgrade" your BIOS to UEFI.

Reality: This is not possible. BIOS and UEFI are two distinct types of firmware with fundamentally different architectures. The ability to use UEFI depends on your motherboard's hardware. You cannot simply download a patch or update that magically turns a BIOS motherboard into a UEFI one. To switch, you must have a motherboard that was manufactured with UEFI support.

3. UEFI’s graphical interface makes it far easier for all users.

Reality: While UEFI generally has a mouse-driven GUI, the complexity of firmware options can still make it intimidating. BIOS’s simpler text interface may be more straightforward for some advanced users who prefer keyboard navigation.

4. UEFI is slower to boot because it has more features.

Reality: UEFI is significantly faster than BIOS. The misconception stems from its complexity, but UEFI's design enables it to initialize hardware in parallel, a process that is much more efficient than the sequential, one-by-one method used by BIOS. This efficiency is a core reason for the much faster boot times on modern PCs.

5. The UEFI specification is too extensive

Reality: Sure, the specification size is extensive, but that just reflects its thoroughness and flexibility to support many platforms, processors, and use cases. Developers implement only the parts necessary for their products.

6. The UEFI platform is just as insecure as the legacy BIOS

Reality: UEFI includes advanced security features like Secure Boot to protect against malware and unauthorized tampering. Systems that do not implement these features may have similar vulnerabilities; however, UEFI technology itself is more secure.

The bottom line

When comparing BIOS and UEFI, it is clear that BIOS has played a big part in the history of computing, but is now limited by its outdated design and hardware constraints. UEFI, on the other hand, offers modern features such as Secure Boot, support for large disk sizes, a graphical interface, and better compatibility with today’s operating systems and hardware.

At the same time, firmware is just one piece of the IT management puzzle. SuperOps brings everything together as an all-in-one IT management platform, enabling MSPs and IT teams to remotely manage thousands of devices with ease. With customizable workflows, proactive monitoring, and real-time updates, SuperOps ensures faster issue resolution and smoother operations. 

Find out what SuperOps can do for your business. Book a demo now. 

FAQs

1. Legacy BIOS vs UEFI BIOS: Which one is better? 

UEFI is preferred for its performance, security, flexibility, and modern hardware support. Legacy BIOS is only relevant for very old systems or through Compatibility Support Module (CSM) emulation in the UEFI firmware. 

2. What happens if I disable UEFI?

If UEFI is disabled even when your system was installed with UEFI, the computer usually will not boot until UEFI is turned back on, which may result in boot errors or lost access to certain security features like Secure Boot.

Additionally, running in legacy mode can increase vulnerability to malware and compatibility problems with modern operating systems and large drives, making it best to keep UEFI enabled.

3. What are the benefits UEFI provides that BIOS does not?

UEFI provides several benefits over BIOS, including much faster boot times, support for hard drives larger than 2 TB, enhanced security with features like Secure Boot, and a user-friendly graphical interface with mouse support.

In addition to that, it offers better compatibility with modern hardware and operating systems, modular extensibility, and improved network capabilities, all of which make UEFI the preferred option for most modern computers.

4. How to know if a computer uses UEFI?

To check if a computer uses UEFI, open System Information (type msinfo32 in the Windows search bar) and look for "BIOS Mode"; if it says "UEFI," your system uses UEFI, and if it says "Legacy," it uses BIOS. 

Alternatively, on Linux, check for the presence of the “/sys/firmware/efi directory”; if it exists, your system uses UEFI; if not, it uses BIOS.

5. How to reset UEFI settings?

You can follow the steps given below to reset UEFI settings:

1. Restart your computer and enter into the UEFI/BIOS setup by pressing the assigned key during boot (often F2, DEL, ESC, or F10).

2. Once in the UEFI interface, look for an option such as “Load Setup Defaults,” “Load Optimized Defaults,” or “Restore Defaults” (which can be found by pressing F9).

3. Confirm the selection to load the default factory settings.

4. Save the changes you have just made and exit the UEFI setup menu (usually by pressing F10 and confirming).

5. Your system will restart with default UEFI settings.

6. What is the difference between UEFI, BIOS, and CMOS?

UEFI is an advanced replacement for BIOS, providing a more advanced, flexible, and secure firmware interface that supports GUI, larger drives, faster boot times, and features like Secure Boot. 

BIOS is the traditional firmware that initializes hardware during boot and provides a basic interface for configuration, stored in a chip on the motherboard. 

CMOS (Complementary Metal-Oxide-Semiconductor) refers to a small, battery-powered memory chip that stores BIOS settings like system time and hardware configurations, keeping them saved even when the PC is off. 

In essence, the difference between BIOS and UEFI and CMOS is that the former two are firmware interfaces, while CMOS is the hardware memory storing the configuration data for that firmware.

7. Why was BIOS replaced by UEFI?

UEFI replaced BIOS because BIOS had many limitations rooted in its old design, such as only supporting drives up to 2.2 TB, operating in slow 16-bit mode with just 1 MB of addressable space, and lacking modern security features. 

UEFI overcomes these limitations by supporting much larger drives, providing faster boot times with 32/64-bit operation, enabling graphical user interfaces, and adding advanced security with Secure Boot.

8. Does UEFI require GPT?

No, UEFI does not necessarily require GPT, but it is the recommended partitioning scheme for UEFI. UEFI can work with MBR, but it has its own limitations. 

Most UEFI-based systems boot from GPT-formatted drives because UEFI requires an EFI System Partition (ESP) that exists only in GPT. However, some UEFI firmware includes a CSM that allows booting from MBR-formatted drives, which are used with Legacy BIOS. Remember that using CSM with MBR disables key UEFI features, including Secure Boot, and limits the drive size to 2 TB.