The classic BIOS is now firmly a relic of the past thanks to Intel’s plans to replace it with UEFI in 2017. But what is UEFI, and how is it different from the BIOS we all know?
BIOS and UEFI: What Do They Do?
Unified Extensible Firmware Interface (UEFI) and BIOS are both low-level software that starts when you boot your PC before booting your operating system, but UEFI supports larger hard drives, faster boot times, more security features, and—conveniently—graphics and mouse cursors, making it a more modern solution.
Newer PCs that ship with UEFI often call it the “BIOS” to avoid confusing traditional PC users. Even so, modern PCs you buy today almost certainly ship with UEFI firmware rather than a BIOS.
BIOS: What Is It?
Basically, BIOS is short for Basic Input-Output System. It’s low-level software that resides on the motherboard of your computer. As soon as you turn on your computer, your BIOS loads, and it starts your computer’s hardware components, checks to see if they’re working properly, and then boots Windows or another operating system.
In the BIOS setup screen, you can configure various settings, including the configuration of your computer’s hardware, the time of your system, and the order in which your computer boots. When you boot your computer, you can access this screen by pressing a specific key-usually Esc, F2, F10, or Delete. When you save a setting, it’s saved to your motherboard’s memory, which is then reloaded by the BIOS.
Before booting your operating system, the BIOS performs a Power-On Self Test. You’ll see an error message or hear cryptic beep codes if something is wrong with your hardware configuration. If something goes wrong, you’ll receive a cryptic series of beeps. Check the manual for more information about the different beep sequences.
During boot-up, the BIOS searches for a Master Boot Record, or MBR, on your boot device, and then launches the bootloader.
Additionally, you may have heard the acronym CMOS, which stands for Complementary Metal Oxide Semiconductor. This is a battery-backed memory system where the BIOS stores various settings on the motherboard. Since flash memory (also known as EEPROM) has replaced this method in modern systems, this method is no longer accurate.
What is the problem with the BIOS?
It has been around for a long time, and hasn’t evolved much over the years. Even MS-DOS PCs released in the 1980s had a BIOS!
Since the days of MS-DOS, the BIOS has evolved and improved. There have been some extensions developed, including ACPI, the Advanced Configuration and Power Interface. As a result, the BIOS can perform advanced power management functions, such as sleep, more easily. Since the days of MS-DOS, however, the BIOS has not advanced as much as other PC technology.
A BIOS can only boot from drives of 2.1 TB or less. 8 TB drives are now common, but a BIOS can’t boot them. That limitation is due to how the Master Boot Record system functions.
When initializing all the hardware interfaces and devices on a modern PC, the BIOS runs in 16-bit processor mode, and has only 1 MB of space to execute in. It has trouble initializing multiple hardware devices simultaneously, which results in slower boot times.
Since 1998, Intel has been working on the Extensible Firmware Interface (EFI) specification. Apple switched to the Intel architecture on its Macs in 2006, but other PC manufacturers did not.
The Unified Extensible Firmware Interface (UEFI) specification was established in 2007 by Intel, AMD, Microsoft, and PC manufacturers. UEFI is an industry-wide standard managed by the Unified Extended Firmware Interface Forum, which isn’t controlled by Intel. Windows Vista Service Pack 1 and Windows 7 introduced UEFI support. A vast majority of computers today use UEFI rather than a traditional BIOS.
The UEFI BIOS replaces and improves the BIOS
It is not possible to switch from BIOS to UEFI on an existing PC. You must purchase new hardware that supports and includes UEFI, as does new hardware. UEFI implementations typically provide BIOS emulation, so you can install and boot old operating systems that need a BIOS instead of UEFI, so they are backwards compatible.
With this new standard, the BIOS is no longer limited by its limitations. By using UEFI’s GPT partitioning scheme instead of MBR, the firmware can boot from drives up to 9.4 zettabytes, which represents an appreciable percentage of all the information on the Internet. As a result, it boots more standardizedly, launching EFI executables rather than code from the master boot record of the drive.
You can boot faster with UEFI since it has a larger addressable address space than BIOS. It also means that UEFI setup screens can be slicker than BIOS setup screens, including graphics and mouse cursor support. However, this is not mandatory. There are still many PCs that ship with text-mode UEFI settings that look and work like old BIOS setup screens.
As part of its Secure Boot functionality, UEFI allows the operating system to be checked for validity to make sure malware has not tampered with the boot process. The UEFI firmware can support networking features as well, allowing it to be configured and troubleshooted remotely. With a traditional BIOS, you need to sit in front of a physical computer in order to configure it.
As an operating system, UEFI does a lot more than a BIOS. It may be stored in flash memory on the motherboard, or it may be loaded from a hard drive or network share at boot time.
The interfaces and features of PCs with UEFI will differ from manufacturer to manufacturer, but the basics will remain the same.
Modern PC UEFI Settings
UEFI computers are faster to boot and shut down than BIOS-based computers, and you can use drives up to 2.2 TB in size. If you’re a normal PC user, you won’t notice the change.
If you need to access low-level settings, there may be a slight difference. You may need to access UEFI settings via the Windows boot options menu rather than pressing a key when the computer starts. Now that PCs boot so quickly, manufacturers don’t want to wait to see if a key is pressed during boot-up to slow down the process. UEFI-equipped PCs can also allow you to access the BIOS by pressing a key during boot-up.
I still see BIOS all the time, why is that?
A number of factors have contributed (or may have contributed) to why the term UEFI hasn’t caught on as much as BIOS on modern computers.
The term BIOS has been in use for decades, and it takes time for millions of people to change their linguistic habits.
- BIOS is easier to say. Most people have heard or would readily guess how “BIOS” is pronounced. But UEFI? How do you pronounce it? Yoo-eee-fee? Yoo-ee-fi? Uh-ee-fi? Yoo-fee? There is no consensus on this either. It will be harder to adopt a term that is hard to say than one that is easy to say.
Since the transition from BIOS to UEFI was mostly behind the scenes and painless, and UEFI performs the same primary functions as BIOS, people didn’t notice it and it doesn’t affect them, so why bother learning the new term?
It may just be one of those terms that stays around for much longer than it is technically accurate, as with “hanging up” a phone.
Most PC users won’t notice-or care-that their new PCs use UEFI instead of a traditional BIOS. They’ll just work better and support more modern hardware and features.