What is UEFI/EFI?

This article explains EFI/UEFI computer and tell you how to determine if a PC is an UEFI PC or a BIOS PC.

UEFI is short for "Unified Extensible Firmware Interface". It’s an advanced interface standard of firmware for operating system compared to legacy BIOS, such as it supports fast PC startup, bootable GPT hard drive, larger capacity more than 2T etc. Almost all recent PCs are EFI/UEFI.

UEFI system architecture

The UEFI specification will be based on the EFI specification (Extensible Firmware Interface) published by Intel with corrections and changes managed by the Unified EFI Forum. UEFI is meant as a replacement for the BIOS firmware interface, present in all IBM PC-compatible personal computers. In practice, most UEFI systems have legacy support for BIOS functions. The UEFI specification is managed by the Unified EFI Forum.

Since UEFI-based computers have bootable information written in their motherboards, you may need to set related hard drive information into your target computer after migrating to a new hard disk. In the contrary, traditional BIOS-based computers don’t need such step: you only need plug a cloned hard drive into a target computer and use it.

To specify if a computer is in UEFI mode, you can make use of the Windows Disk Management tool.

If the type of the hard drive where system partition resides is GPT, like the above picture shows (EFI System Partition), your computer is in UEFI mode. If it is MBR, your computer is the traditional BIOS mode