→ Bios vs uefi bios: what is it and the main differences?

Today's computers use UEFI firmware instead of traditional BIOS. These two types of firmwares are low-level software that is started by turning on the PC before the operating system loads, but the UEFI (Unified Extensible Firmware Interface) is a more current solution, which allows the use of larger hard drives, Faster boot times, more security features and graphics and mouse management.

Sometimes new PCs shipped with UEFI still prefer to use the term "BIOS" to avoid confusing people who are used to a PC with a traditional BIOS.

BIOS and UEFI (the replacement of BIOS) are essential components for the operation of our computer. They act as true intermediaries between the computer hardware and the operating system. Without them, an operating system like Windows would not be able to detect and use your installed devices.

Index of contents

What is BIOS and how does it work?

BIOS stands for Basic Input-Output System. It is low-level software found on a chip on the computer's motherboard.

This software will be loaded when the computer starts and will be responsible for activating the hardware components of the computer, ensuring proper operation, and then running the bootloader that starts Windows or any other operating system that you have installed.

Various options can be configured on the BIOS setup screen. Settings like computer hardware settings, system time, and boot order can be found here.

You can access this screen by pressing a different specific key depending on the type of computer you have, but the Esc, F2, F10 or Delete keys are often used while the computer is starting up.

When you save a setting, it is saved in the memory of the motherboard itself. When you start the computer, the BIOS will configure the computer with the saved settings.

How does BIOS work?

The BIOS goes through a POST (Power-On Self Test), before booting the operating system. Check that the hardware configuration is valid and that it works correctly. If something goes wrong, you will see an error message or hear a series of beep codes emitted from the internal speakers. You will have to find out what the different beeping sequences mean in your computer manual.

When the computer starts, and after the POST function is complete, the BIOS looks for a Master Boot Record (MBR) stored on the boot device and uses it to start the bootloader.

The Basic Input Output System is a firmware exclusive to IBM machines that has the following functions:

Initialize all components of the chipset motherboard and some peripherals. Identify all internal and external devices connected to it. If it does not, initialize the priority order of the input devices. Start the operating system present on the first peripheral. available.

Basically located on a ROM chip, in modern PCs, the BIOS is in a flash memory that allows it to be accessed and modified by the user during updates, for example.

In previous versions of PCs like MS-DOS, the BIOS provided the link with external devices (mouse, keyboard, etc.) and the operating system. Now, with the latest versions of Windows in particular, the operating system itself is capable of managing the hardware, so that once the operating system starts, the BIOS can almost be on standby and be reused.

CMOS memory

You can also see the acronym CMOS, which stands for “Complementary Metal Oxide Semiconductor”. This refers to the memory of the battery where the BIOS stores various parameters on the motherboard. Actually, this term is obsolete, because this method has been replaced by flash memory (also called EEPROM) in current systems.

The BIOS starts by looking at the options saved in the CMOS (nonvolatile BIOS memory) that determine how the user wants the machine to boot.

The poor evolution of the BIOS

The BIOS has been around for quite some time, however it has not advanced in depth. Even computers using MS-DOS that were manufactured in the 1980s already had a BIOS.

Of course, the BIOS has improved and evolved somewhat over the years. For example, several extensions have been designed, including ACPI (Advanced Configuration and Power Interface).

This makes it easy for the BIOS to configure devices as well as perform advanced power management features such as sleep.

Although the BIOS has not known the least notable advance when compared to other PC technologies since the days of MS-DOS.

The traditional BIOS still has multiple limitations. It can only boot from drives of 2.1TB or less. 3TB drives are now common and a computer with a BIOS cannot boot from them. This limitation is due to the way the BIOS main boot system works.

The BIOS must be running in 16-bit processor mode and only has 1 MB of space to run. It is difficult to initialize multiple hardware devices at once, resulting in a slower boot process by initializing all interfaces and hardware devices on a modern PC system.

This outdated BIOS should have been replaced several years ago. Intel began development of the Extensible Firmware Interface (EFI) specification in 1998. Apple chose EFI when it changed the Intel architecture on its Macs in 2006, but other PC manufacturers did not follow suit.

In 2007, manufacturers Apple, Dell, Intel, Lenovo, AMD and Microsoft agreed on a new specification UEFI (Unified Extensible Firmware Interface). It is an industry-wide standard administered by the Unified Extended Firmware Interface Forum, and is not solely managed by Intel.

UEFI support was introduced in Windows with Windows Vista Service Pack 1 and Windows 7. The vast majority of computers you can buy today use UEFI instead of traditional BIOS.

BIOS setup

The first image people have of the BIOS is a stark blue screen that shows things in English. It is true that at first glance, the BIOS is not very intuitive and does not invite people to configure their system. However, we should not stop at this first impression, as it is really very easy to use.

The main thing to know is that each computer and motherboard manufacturer uses a different BIOS. There is not a single BIOS, but several variants of it.

Each manufacturer offers its own characteristics and parameters depending on the processor and chipset supported by the motherboard. This is the reason why the same parameters are often not found from one BIOS to another. However, once you understand how to configure a BIOS, you can easily configure it on a different motherboard.

To access the BIOS settings, turn on the computer and, when it starts the BIOS, select the BIOS Settings option by pressing the corresponding key. Note: The key is specific to the motherboard model, so you should look at the bottom of the screen to see the correct key you should press (in most cases it is the Fn key , Delete / DEL / F1 / F2 or Esc).

If you make changes to the BIOS, you must save them to take them into account. If you restart the computer without saving the configuration with Save & Exit Setup, the changes will be lost.

You have to be careful when modifying the BIOS, since a bad configuration can make your system unstable.

Since the documentation for any motherboard is always quite detailed, it is a good idea to download and read it carefully. If you think you have done something wrong or if you want to return to the factory settings of your BIOS, select the Load Fail-Safe Defaults or Load Optimized Defaults option.

These are the parameters that you will usually find when accessing the blue screen:

- Standard CMOS Features: menu that allows defining the date, time and specifications of hard drives and disk drives. By default, the BIOS automatically detects the disks and disk drives connected to the motherboard, so there is no need to manually enter the motherboard model.

However, you can manually enter the specifications of your hard drive or drives to speed up the startup of the computer.

- Advanced BIOS Features: used to choose the boot order of the device, whether or not to show a logo, hide the classic BIOS screen, cancel the RAM test (Quick Power On Self Test), and more.

- Integrated Peripherals: contains the configuration of the devices integrated in the motherboard (audio, LAN and USB ports). Unused (and still enabled) ports use a lot of system resources and should be disabled.

- Power Management Setup: If the settings in this menu are not configured correctly, the system may not shutdown properly, or you may have problems with sleep mode. Since Windows already includes power management, it is best to disable all power management in the BIOS. Otherwise, there may be conflicts between the BIOS and Windows Power Management.

- PC Health Status: allows to know the temperature of the processor and the motherboard, to know the rotation speed of the hard disk or its fans and much more.

- Load Fail-Safe Defaults: Loads the default BIOS settings, adjusting the performance level to a minimum to achieve optimal stability.

- Load Optimized Defaults: Loads the default BIOS settings, optimally adjusting the settings for best performance.

- Set Password: set a password to access the BIOS settings.

- Save & Exit Setup: save the changes made and restart the computer.

- Exit Without Saving: exits the BIOS without saving the changes made.

What is the UEFI BIOS?

It is an intermediate software between the firmware and the operating system. UEFI replaces traditional PC BIOS on the latest computer models. However, there is no way to switch from BIOS to UEFI on an existing PC.

For that, you must purchase new hardware that supports and includes UEFI, as most new computers do. Most UEFI implementations provide BIOS emulation, so you can choose to install and boot older operating systems that expect BIOS instead of UEFI, so they are compatible with older systems.

This new standard avoids the limitations of the BIOS. UEFI firmware can boot from 2.2TB or larger drives. In fact, the theoretical limit is 9.4 zettabytes . This is approximately three times the estimated size of all data on the internet, because the UEFI uses the GPT partitioning scheme instead of MBR.

Also, it starts the computer in a more standardized way, by running EFI instead of executing the code for the main boot record of a drive.

The UEFI can operate in 32 or 64 bit mode and has a higher address range than the BIOS, which means that it boots faster. This also means that UEFI configuration screens can be smoother than BIOS configuration screens, including graphics and mouse cursor support.

However, this is not mandatory. Many PCs still come with text-mode UEFI configuration interfaces that look and function like an old BIOS setup screen.

UEFI has other features too. It supports secure boot, which means that the operating system can check its validity to make sure that no malware has altered the boot process.

It can support network functionality directly in the UEFI firmware itself, which can assist in remote troubleshooting and configuration. With a traditional BIOS, you must be sitting in front of a physical computer to configure it.

It is not just a replacement for the BIOS. UEFI is essentially a small operating system that runs on PC firmware, and can do much more than a BIOS. It can be stored in the flash memory of the motherboard, or it can be loaded from a hard drive or a shared network at boot time.

Different computers with UEFI will have different interfaces and features. It all depends on the manufacturer of the PC, although the bases will be identical on each PC.

To boot a UEFI compliant operating system and take advantage of these new features, the UEFI standard requires the hard disk to use the GPT partition table (GUID Partition Table).

The UEFI can also boot to a hard drive using the MBR partitioning table, but this backward compatibility involves disabling the UEFI and emulating a traditional BIOS (via the CSM option). As a result, you will no longer benefit from the new benefits offered by UEFI.

The limits of the old MBR

The MBR (Master Boot Record) was first introduced with IBM PC DOS 2.0 in 1983. It is named because the MBR is a special boot sector located at the beginning of a drive. This area contains a bootloader for the installed operating system and information about the logical partitions of the drive.

The bootloader is small code that normally loads the largest bootloader from another partition onto a drive. If you installed Windows, the initial bits of the Windows bootloader will reside here, so you'll need to repair the MBR if it's overwritten and Windows won't boot. If you have Linux installed, the GRUB boot loader will normally be located on the MBR.

The advantages of the GPT

GPT (GUID Partition Table) is a newer standard that is gradually replacing MBR. In turn, it replaces the old MBR partition system with something more modern. It gets this name because each partition on the drive has a "global unique identifier" or GUID: a random string so long that every GPT partition on the planet probably has its own unique identifier.

The GPT also records Cyclic Redundancy Code (CRC) values to verify that your data is intact. If the data is corrupted, the GPT may notice the problem and try to retrieve the corrupted data from another location on the disk.

On the other hand, the MBR had no way of knowing if the data was corrupted - it just looked to see if there was a problem when the boot process failed or if the drive's partitions disappeared.

Access UEFI parameters

If you are a normal PC user, switching to a UEFI computer will not be a noticeable change. The new computer will start and shutdown faster than with a BIOS, and you'll be able to use 2.2TB or larger drives.

But if you need to access the UEFI settings, there may be a little difference. You may need to access the UEFI setup screen through the Windows Startup Options menu instead of pressing a key while the computer is starting up.

To start computers faster, equipment manufacturers do not want to slow down the startup process until they see if the user presses a key.

But there are still PCs with UEFI that allow access to the BIOS in the same way, by pressing a key during the boot process, it all depends on the manufacturer.

UEFI Configuration

Very similar to the BIOS interface in terms of functions, but very different in terms of interface, in the UEFI you can start by viewing a main page, from where you can get an overview of the system with the BIOS version, the processor type, RAM size and more.

We can also get data on system performance, processor and motherboard temperature, voltage, or fan rotation speed. You can also change the boot order of computer devices by dragging and dropping with the mouse.

By accessing the advanced mode of the UEFI, the following functions can be accessed, always bearing in mind that it may vary from one manufacturer to another:

Main: Displays global system information, adjusts BIOS date, time, and language AI Tweaker: Adjusts processor and RAM performance (overclocking) Advanced: Processor settings, SATA, USB, PCH settings, enable or disable built-in devices.Monitor: shows processor and motherboard temperature, fan rotation speed. You can also manually adjust the rotation speed of the tower or processor fans. Startup: Allows you to set the device boot order, logo display, and digital lock. Tool: Utility to flash UEFI BIOS.

Final words and conclusion about BIOS vs UEFI BIOS

While the UEFI is a big update, it's largely in the background. Most PC users will never notice or have to deal with their new PCs using UEFI instead of a traditional BIOS. They will simply perform better, support more modern hardware and functionality.

Despite its many advantages, the UEFI system is still very critical and most of the time due to the advantages it offers:

Secure boot that does not allow a free operating system. New tools too close to an operating system interface. Multiple boot problems.

Like BIOS, UEFI tools are still tricky for newbies, and poor configuration can always lead to the motherboard being completely locked.

We recommend reading the following articles:

So it is essential to correctly configure the UEFI. Unfortunately, users are often confused by BIOS and UEFI settings that give access to options that are not easy to understand.