UEFI vs LEGACY ? What is the difference?

uefi and legacy

What is UEFI and Legacy boot? well the difference between UEFI and LEGACY boot is the process that firmware uses to find to boot target. Legacy boot is the boot process used by BIOS(BASIC INPUT OUTPUT SYSTEM) firmware. Firmware maintains a list of installed storage devices that may be bootable ( Hard Drives, Optical Disk Drives and etc) enumerates them in a configurable order of priority. Legacy used the MASTER BOOT RECORD (MBR) and UEFI uses GUID (GPT). Once the POST(Power On Self Test) procedure completed the firmware loads the first sector of each of the storage targets memory and scans it for valid MBR. If a valid MBR found the firmware passes execution to the boot loader to select a partition to boot from. If one is not found it proceeds to next device in boot order.

UEFI or Unified extensible firmware interface is a modern way of handling the boot process. UEFI stores the boot data in a .efi file rather than the firmware. During the POST procedure post the UEFI firmware scans all of the bootable storage devices that are connected to the system for a valid guid partition table like MBR GPT doesn’t contain boot loader. The firmware scans for all of the bootable storage devices that are connected to the system service partition to boot from. If no efi bootable partition found the firmware fall back to legacy mode.

UEFI runs in 32-bit and 64-bit allowing support for mouse and touch navigation while Legacy runs in 16-bit mode that only supports keyboard navigation. UEFI offers secure boot which can prevent boot-time viruses from loading and legacy does not provide a secure boot method which allows for the loading of unauthorized applications. For legacy max size partition size is 2 Tera Bytes while UEFI max partition size is 9 Zeta Bytes. For when it comes to partitions MBR can have max 4 primary partitions and GPT can have 128 partitions

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