What is UEFI or Unified Extensible Firmware Interface?

At Computex, Michael Angiulo of Microsoft took the stage to give a demo of Windows 8. One of the notable things he mentioned was, the requirement of UEFI to run Windows on ARM based tablets.


What is UEFI

UEFI is the acronym for Unified Extensible Firmware interface. It is basically a replacement for BIOS which is used to set up the hardware and load and start an operating system in today’s Windows 10/8 PCs.

The ancestor of UEFI was developed by Intel for their Itanium based servers. The main limitation of BIOS was that it was a 16-bit with just 1 MB of addressable space and utilized Master Boot Record (MBR) partition scheme. Thus there were constraints on the amount of RAM that could be used by BIOS and it couldn’t support an HDD with a capacity of above 2.2TB. In order to overcome these limitations, Intel introduced the Intel Boot Initiative which was later renamed as EFI. It was then taken over by the Unified EFI Forum, which evolved it into UEFI.

The original EFI interface is used in Macs and only supports Intel processors. But UEFI on the other hand supports both Intel and AMD processors.

Advantages of UEFI

UEFI supports both 32-bit and 64-bit architecture. Thus it can utilize more RAM to do more complex processes than BIOS. UEFI also support CPU independent architecture and drivers.

Unlike BIOS, UEFI can have a more visually pleasing interface that supports mouse. See the Asus UEFI interface below.

Apart from the standard MBR partition scheme, UEFI also supports GUID Partition Table or GPT. GPT allows for a maximum disk and partition size of 9.4 ZB (compared to 2.2TB of MBR) and 128 partitions on Windows (compared to 4 of MBR).

UEFI comes with a boot manager which removes the needs for a separate boot loader. UEFI also supports extensions such as ACPI that are not 16-bit. Besides, UEFI also gives you faster start-ups and better networking support.

With the advancement in the hardware industry, BIOS is becoming more and more insufficient to handle the power and capacities of today’s machines and UEFI has the capability to handle our ever-growing thirst for more computing power at least for the next two decades.

In general, UEFI-enabled machines have faster startup and shutdown times as compared to BIOS-based machines. Here is a list of Windows 10 features that requires UEFI:

  • Secure Boot protects Windows 10 pre-boot process against bootkit and other malware attacks.
  • Early Launch Anti-malware (ELAM) driver gets loaded by by Secure boot first and checks all non-Microsoft drivers before they are loaded.
  • Windows Trusted Boot protects the kernel and system drivers during launch.
  • Measured Boot will measure components from firmware till the boot start drivers & stores these measurements in the TPM chip.
  • Device Guard uses CPU virtualization and TPM support to support Device Guard with AppLocker, and Device Guard with Credential Guard.
  • Credential Guard works with Device Guard and uses CPU virtualization and TPM support to protect security information like NTLM hashes, etc.
  • BitLocker Network Unlock will automatically unlock Windows 10 at reboot when connected to a corporate network.
  • GUID Partition Table or GPT disk partitioning is required to enable large boot disks.

Hopefully more manufacturers will switch to UEFI from BIOS.

Check if your PC supports UEFI or BIOS.

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Currently pursuing Bachelors in Electronics, the author Nithin Ramesh is a technology blogger. Apart from technology his other interests include cricket and rock music.