How a Computer Boots?
How a Computer Boots?
Before diving deep into what UEFI and Legacy Boot modes are, let us discuss how a computer boots. Understanding this will help clear up some concepts.
When you turn on your computer, it powers on the CPU, the key computer component that processes commands or instructions.
However, at this stage of the boot-up process, there are no instructions loaded into the memory. As such, the CPU switches to the system firmware, which contains instructions for the boot process.
The firmware code performs a Power On Self Test (POST) initialization and sets up all the connected peripherals. Once the POST check is successful, the firmware loads the storage devices and checks for a boot loader. The firmware then switches the instructions to the bootloader to handle the boot process.
At this stage, the bootloader, such as LILO and GRUB, takes over, loads the system kernel in the memory, and initializes required processes.
As mentioned, the firmware helps handle hardware initialization during the boot-up process. This firmware is commonly known as BIOS or Basic Input Output System.
What is Legacy Boot?
Legacy Boot refers to the boot process used by the BIOS firmware to initialize hardware devices. The Legacy boot contains a selection of installed devices that get initialized as the computer performs the POST test during the boot process. The legacy boot will check for all connected devices for the Master Boot Record (MBR), usually in the first sector of a disk.
When it can’t find a bootloader in the devices, Legacy switches to the next device in the list and keeps repeating this process until it finds a bootloader, or if not, returns an error.
What is UEFI?
UEFI or Unified Extensible Firmware Interface is a modern way of handling the boot process. UEFI is similar to Legacy, however, it stores the boot data in a .efi file rather than the firmware.
You will often find UEFI boot mode in modern motherboards with very intuitive and user-friendly Interfaces. UEFI boot mode contains a special EFI partition that is used to store the .efi file and is used in the boot process and the bootloader.
Difference between UEFI and Legacy
At a base level, UEFI and Legacy are very similar. However, on a deeper level, they’re also different.
Since UEFI is a BIOS successor, it has better functionalities and features. The following are the differences between UEFI and Legacy:
Although UEFI may sound better than Legacy (and it is), it’s not always the best choice to use, and you may not need it.
In some cases, you may have to use Legacy, depending on the features you want. For example, if you want dual booting, UEFI can hinder this process.
Here are other scenarios where you might not need UEFI:
1. Dual Booting process
2. When you have less than 2 TB of storage device (stick to MBR)
3. When your OS does not need to write code to interact with the hardware
4. If you need a quick and simpler GUI that you can control with a keyboard.