UEFI vs. traditional BIOS firmware

UEFI: Unified Extensible Firmware Interface

BIOS: Basic Input/output System

The advantages of UEFI

·         A powerful pre-boot environment capable of running applications

·         Modular design

·         CPU-independent architecture (Itanium, x86, x86-64, ARM Arch32, Arm Arch64)

·         BIOS interface compatibility and legacy booting

·         The ability to boot from disks larger than 2TiB (note the difference between 2TB and 2TiB)

MBR: Master Boot Record

GPT: GUID Partition Table

ESP: EFI System Partition

The legacy BIOS systems are only able to boot from MBR partition tables (there are exceptions, but this is generally a rule) and the MBR specification can only address up to 2TiB of disk space, which results in a BIOS system only being able to boot from disks of 2TiB or smaller.

Other disadvantages of MBR formatted disks include a limited number of bootable partitions and a single pointer to a bootloader/boot manager.

The GPT specification allowed the disks of significantly larger size (several orders of magnitude, up to Zettabytes in size) due to its larger bit allotment for partition addressing, 64B instead of the 16B used by MBR. GPT can partition disks of varying sizes depending on the sector size. This is due GPT addressing sectors as opposed to individual bits or bytes.