Changing an Existing Firmware Requires Knowledge of Special Programs and Techniques

What is Unified Extensible Firmware Interface (UEFI)?

Unified Extensible Firmware Interface (UEFI) is a specification for a software program that connects a reckoner’s
firmware
to its operating system (
OS
). UEFI is expected to eventually supercede basic input/output system (
BIOS
) only is compatible with information technology. The specification is most often pronounced by naming the letters U-Eastward-F-I.

UEFI functions via special firmware installed on a estimator’south
motherboard. Like BIOS, UEFI is installed at the time of manufacturing and is the first program that runs when booting a computer. Information technology checks to see which hardware components are attached, wakes upwardly the components and hands them over to the OS. The new specification addresses several limitations of BIOS, including restrictions on hard disk

partition

size and the amount of fourth dimension BIOS takes to perform its tasks.

Most modern figurer systems are equipped to support traditional BIOS, besides as UEFI, although Intel Corp. has stated its intention to phase out BIOS support in newer personal computers (PCs).

What does UEFI do?

UEFI defines a new method by which OSes and platform firmware communicate, providing a lightweight BIOS culling that uses only the data needed to launch the OS boot process. In addition, UEFI provides enhanced calculator security features and supports about existing BIOS systems with
backward compatibility.

UEFI contains platform-related data tables and boot and
runtime
service calls used past the Bone loader. Taken together, this information defines the required interfaces and structures that must exist implemented for firmware and hardware devices to support UEFI. UEFI is programmable, enabling
original equipment manufacturer
developers to add applications and drivers and UEFI to function every bit a lightweight OS.

In general, BIOS is considered a vestige from earlier computing, whereas UEFI is regarded as the wave of the future. All the same, for ease of understanding, some information technology users refer to the processes collectively as
UEFI BIOS, despite their substantial differences.

UEFI’south evolution from EFI

BIOS has been in apply since the advent of
disk Bone
computers in the mid-1970s. In 1981, IBM was the get-go vendor to incorporate BIOS in PCs, a move that prompted wide industry adoption. The emergence of UEFI parallels the increased drive densities used for modern awarding workloads.

Intel developed the Extensible Firmware Interface (EFI) every bit an outgrowth of its 64-bit Itanium server architecture in the 1990s, a technology codeveloped with estimator maker Hewlett Packard (HP). The industry perceived EFI as a manner to address the memory and processing limitations of BIOS in
x86
server architectures. Those limitations included 16-bit computing manner, bounded system retentivity and dull associates language programming.

EFI, subsequently renamed Intel Kick Initiative, technically remains the property of Intel, although the vendor ceased sole evolution of the specification post-obit the release of EFI version 1.10 in 2005. (Past and then, Intel had too phased out its Itanium processor line, following product delays and other hiccups.) Intel contributed EFI 1.10 to the
UEFI Forum, an alliance of chipset, hardware, system, firmware and Bone vendors.

The industry consortium manages the development of UEFI specification standards. The latest standard, UEFI 2.ix, was made publicly available in March 2021.

Booting up: BIOS vs. UEFI

Turning on a computer kick-starts a chain of events that occurs before the Bone is loaded. Firmware rouses the computer’s subsystem to execute a series of tests and locates the
boot loader, which, in plough, starts the OS kernel.

BIOS and UEFI both utilize low-level software to manage startup functions prior to booting an Bone, albeit using different techniques.

BIOS resides on a chip on the machine’s motherboard and initializes the central processing unit, random access memory, Peripheral Component Interconnect Express cards and network devices. BIOS runs a power-on self-examination (Post) diagnostic sequence. POST ensures that hardware is configured properly and all components are functioning every bit intended.

BIOS runs only in 16-bit processor mode, which limits the number of software commands the firmware is able to execute at any once. BIOS allots 1 megabyte of memory in which tasks can be executed. Interfaces and devices thus are initialized sequentially, which tin can contribute to a sluggish startup.

To attain its chore, BIOS consults the Master Boot Record (MBR) to locate the Bone and launch the kick loader. MBR uses 32-bit values to describe the offset and length of a partition, thus limiting BIOS systems to ii terabyte (TB) drives and no more four partitions.

UEFI behaves similar a like a miniaturized Os that sits betwixt firmware and the OS. It performs the same diagnostics every bit BIOS at startup but offers more flexibility. The OS boots directly in UEFI. This eliminates the need to repeatedly press toggle keys, as is required to kicking BIOS.

UEFI stores initialization data in an EFI file partition in
nonvolatile wink memory, rather than in the firmware. UEFI besides can load during boot from a drive or a network share. UEFI too deploys a more flexible partitioning scheme than MBR, known every bit a Globally Unique Identifier Partition Table, or GPT. GPT was also created past Intel as part of EFI. GPT uses 64-bit values to enable the creation of up to 128 partitions and is required for systems launched from two TB drives and larger. The EFI sectionalization uses the
file allotment table, including FAT16, FAT32 or virtual Fatty.

Most new desktop PCs, laptops and some tablets bundle UEFI firmware that runs in compatibility support mode for older 32-bit Windows. Estimator manufacturers are expected to back up BIOS in the near term, but the transition to UEFI is well underway. In 2013, custody of the Advanced Configuration and Power Interface (ACPI) was transferred to UEFI Forum.

Originally developed collaboratively by HP, Intel, Microsoft, Phoenix Technologies and Toshiba, ACPI is an open standard for BIOS that governs how much power is delivered to each peripheral device.

Motherboard- or system-specific utilities for accessing UEFI/BIOS differ from vendor to vendor and how they appear but vary little in terms of functionality.

Advantages of UEFI

UEFI provides many significant enhancements over BIOS, including the following:

• Boot manner.
  Microsoft Windows users can run 32-bit UEFI or 64-bit UEFI, although experts recommend that the Bone bit mode and the firmware fleck way should be the same to avoid communication problems during runtime.
• Drives.
  According to UEFI Forum, UEFI supports boot drives of two.2 TB and higher capacities, including drives with theoretical capacity of ix.4
  zettabytes. That far exceeds the maximum drive capacities currently available.
• Drivers.
  UEFI supports discrete drivers, whereas BIOS drive support is stored in
  read-only memory, which necessitates tuning information technology for compatibility when drives are swapped out or changes are made.
• Graphical user interface (GUI).
  UEFI enables new modules to be added to the GUI more easily, including device drivers for motherboard hardware and attached peripheral devices.
• Multiple OS back up.
  Whereas BIOS allows a single boot loader, UEFI lets users install loaders for
  Debian-based Ubuntu and other Linux variants, along with Windows OS loaders, in the aforementioned EFI system segmentation.
• Programming.
  UEFI firmware is written predominantly in
  C
  language, which enables users to add or remove functions with less programming than BIOS, which is written in an
  assembler
  language, sometimes in combination with C.
• Security.
  Secure Kick is a UEFI protocol for Windows eight or afterward Windows versions. Secure Boot makes a arrangement’s firmware the root of trust to verify device and system integrity. The goal is to prevent hackers from installing
  rootkits
  in the time betwixt bootup and handoff to the OS. Secure Boot also enables an authorized user to configure networks and troubleshoot issues remotely, something a BIOS ambassador must be physically present to do.

As computer makers gradually motion away from BIOS, they typically integrate UEFI firmware that runs with Compatibility Support Module (CSM) in modern devices. Although non intended as a long-term solution, CSM enables UEFI-based machines to launch in legacy BIOS manner to work with older Windows versions and other OSes. All the same, users may find it preferable to upgrade to the latest version of the OS to realize the value of UEFI.

UEFI disadvantages, or when to boot from BIOS

Software is always a target for threat actors, and UEFI is no exception. I such attack, dubbed
TrickBot, surfaced in December 2020. TrickBot malware works past attempting to spy on device firmware, which could permit malicious actors to subvert the kick process and proceeds admission to the Os.

The TrickBot
episode
came on the heels of 2018 findings by ESET Research, a Slovak outlet for the information security community, which claimed to take discovered a rootkit in the wild that potentially enabled hackers to surveil UEFI firmware and install malicious code.

Aside from security issues, organizations switching to UEFI may incur a toll related to booting from
flash. While this is faster than booting from
hard disk drives, older systems may require a retrofit, namely a larger flash die on the motherboard.

Another potential drawback is UEFI’due south reliance on the FAT file format, which is maintained past the Bone. Larger drive partitions can add together too much organisation overhead, thus defeating some of the performance advantages. This is an case in which BIOS can be a more than useful pick, especially for a computer running an older OS version and smaller boot disks.

UEFI accessibility

Users tin can download the UEFI specification from the UEFI Forum website. The most contempo version, UEFI 2.ix, features several enhancements, including the following:

• supports devices based on the new
  Compute Limited Link
  interconnect;
• supports publishing Linux Device Tree Blob binary format files that place computer components in the UEFI configuration table; and
• clarifies how UEFI-based update runtime calls are made on certain
  Advanced Reduced Pedagogy Ready Calculating Machine server

To determine whether a computer boots from BIOS or UEFI, press the
Windows
and
R
keys on the keyboard to launch the Run configuration box. Type
MSInfo32
in the dialog box, and striking the
Enter
primal. A system summary screen appears. Look for the entry entitled
BIOS Style, and make annotation of the corresponding value. If the value says
Legacy, the system has BIOS. Otherwise,
UEFI
volition appear in the value field.

Windows users can access UEFI via the PC Settings pick in the search bar. The path is PC Settings > Update & Security > Recovery > Advanced Startup, and select the
Restart At present
option. From the menu, select Troubleshoot > Avant-garde Options > UEFI Firmware Settings, and restart once more.

Linux machines with UEFI installed will evidence information technology in the sys/firmware/efi directory. This will besides be reflected in the Linux
1000 Unified Bootloader
boot managing director every bit
grub-efi, rather than
grub-pc
for BIOS.

Coreboot and UEFI

With the manufacture gradually phasing BIOS out, UEFI receives most of the attention as the heir apparent. However, open source Coreboot is another choice vying to replace legacy BIOS, and its proponents merits it is faster than UEFI. Coreboot, formerly known as LinuxBIOS, is purportedly able to replace proprietary BIOS and UEFI firmware — with underlying benefits of extreme operation, minimal resources to boot machines and security measures that include a minimal
trusted computing base
and virtual boot disk.

Coreboot code was first introduced in 1999, and the community-based evolution project’s supporters include Google, whose
Chromebook
devices replaced BIOS with Coreboot since the first generation. Coreboot’south market penetration has been slow, however, due to the work it entails on the part of manufacturers. Since Coreboot initializes only Bare metal, device makers demand to brand the try to port the code for integration in chips and motherboards.