What is BIOS?
BIOS is a type of firmware which interacts with a computers processor and allows for it to begin the boot cycle.
BIOS stands for “basic input/output system” and it oversees the flow of data between the operating systems attached devices and adapters.
The BIOS firmware is included in your systems motherboard which is stored on a small memory chip of the motherboard.
You can interact with BIOS during the boot process to edit settings such as which disk is to be loaded as default on boot as well as many other settings dealing with the CPU and so forth.
Boot Process of BIOS
When the boot cycle begins BIOS will first initialize hardware such as your CPU and RAM then it will proceed to run a POST (Power On Self Test) which is a series of tests to ensure your computer’s hardware is functioning properly.
After the Power On Self Test, BIOS will then determine the boot order by detecting bootable devices then BIOS loads a program called “the boot loader” which handles loading the operating system into memory.
Once finished being loaded, the boot loader will then transfer remaining startup tasks over to the operating system itself which will then begin normal startup.
What is UEFI?
UEFI is a newer type of firmware and much like BIOS also allows for a computer system to begin and move through the boot process.
UEFI stands for “Unified Extensible Firmware Interface” and it quite similar to BIOS except it is a newer spin off the old BIOS firmware and offers more features.
Such features of the UEFI firmware involve being able to support larger disks, faster system boot times, secure booting, password protection, GPT partition support, and a GUI (graphical user interface) for configurations.
Boot Process of UEFI
The UEFI boot process is a bit more complex than BIOS. At the start of Power On the firmware begins to initialize hardware, CPU, and memory.
Following that phase drivers are loaded and then able to communicate with the hardware of the system.
Once drivers are able to communicate with the hardware, the UEFI firmware searches for bootable devices and provides a selection of options for boot, such as disks, usb drives, ect.
After the boot device is selected there and security checks have finished, the boot loader will then pass over to the operating system which then begins to load.
BIOS vs UEFI (features of UEFI in comparison)
Ultimately UEFI was created to resolve limitations of BIOS and to provide additional features for modern hardware on computers.
The basic difference between the BIOS and UEFI is that with UEFI you can use disks/partitions over 2TB in size and the boot process is slightly more complex but faster for larger disks.
We’ll talk more about some features offered with UEFI below to showcase why the differences between BIOS and UEFI.
System Security with UEFI
UEFI offers robust security features which are not offered in legacy BIOS which makes the Unified Extensible Firmware Interface (UEFI) more desirable as a firmware option.
Secure Boot
Secure boot is feature only offered with UEFI which makes sure only trusted software and code is able to execute during the boot process.
How does Secure Boot work with UEFI?
Secure boot allows for only trusted code to run on boot by verifying that code through digital signatures and this verification takes place during the beginning of the boot cycle.
If the verification does not pass its checks then UEFI will not proceed to load the boot loader.
Overall this feature works in the prevention of malware being able to execute any code during the boot process since only trusted software component code is allowed to load.
Password Protection
Another great security feature of UEFI is that it offers password protection to restrict access to unauthorized users.
How does Password Protection with UEFI work?
When enabled it requires a password before accessing the BIOS or UEFI settings or even before booting the system in general.
This protection feature will prevent users from booting into the system using removable media or making changes to the BIOS settings.
Additional features of UEFI
System Performance with UEFI
UEFI offers enhanced performance through its device initialization and memory management.
The UEFI firmware runs in 32 or 64-bit mode which allows for all of the systems memory to be accessible during the boot cycle and in turn allows for devices to be initialized at a faster rate.
In comparison, BIOS only operates in 16-bit mode which means the device initialization process is not as fast since it can only access a small portion of RAM on startup.
Partition Support with UEFI
Another key difference is that UEFI supports GPT partitions (GUID Partition Table) which is a new modern standard for partitions on modern computers used these days where as BIOS supports MBR (Master Boot Record partition structure).
When we compare BIOS to UEFI in this aspect, MBR (the BIOS firmware partition structure) is limited to hard disk sizes of 2TB in size where as GPT (used by UEFI) does not have this limitation and can support partitions over 2TB.
Graphical User Interface with UEFI
UEFI and BIOS both offer the ability to interact with their graphical user interface for adjustments to hardware settings, boot order ect.
However within the UEFI firmware interface we’re able to more easily navigate through settings to adjust advanced features using mouse and keyboard which when compared to BIOS we were only able to navigate using keyboard since it BIOS does not offer mouse support.
EFI System Partition (UEFI) vs MBR (BIOS)
When comparing UEFI and BIOS with where boot loader information is kept, with UEFI it stores boot loader information and other needed files for startup within the EFI System Partition (Extensible Firmware Interface) which is a dedicated partition.
On the flip side with BIOS this information is not stored and it instead loads the first sector of a bootable device called the Master Boot Record (MBR).
Switching from UEFI to Legacy BIOS Mode
Some users may still require to use BIOS for compatibility reasons with hardware components used on their machines or older operating systems and in such cases you are able to switch to the Legacy BIOS Mode from UEFI.
This can be done by accessing the firmware settings interface by interrupting boot with common keys such as DEL, F2, F11 (depends on the motherboard manufacturer) and updating the boot mode within the boot settings menu.
Conclusion
BIOS and UEFI are very similar and both function well so it really depends on your situation for which firmware to use on your personal computer.
For example BIOS would be just fine if you’re not needing to use disks over the size of 2TB and do not wish to edit any settings within the firmware but if you do require this you’d want to use UEFI instead.
However if you’re using large disks (over 2TB) and prefer to have added security features then it may be more attractive to stick with the UEFI firmware.
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