What does uefi mean?

uefi's full name is "Unified Extensible Firmware Interface", which is a standard that describes a type of interface in detail. This interface is used for the operating system to automatically load from a pre-boot operating environment to an operating system; uefi is a personal computer system specification used to define the software interface between the operating system and system firmware as a replacement for BIOS plan. The extensible firmware interface is responsible for power-on self-test (POST), contacting the operating system, and providing an interface between the operating system and the hardware.

The operating environment of this tutorial: Windows 7 system, Dell G3 computer.

What is uefi

UEFI, the full name is "Unified Extensible Firmware Interface" (Unified Extensible Firmware Interface), is a detailed description Standard for type interfaces. This interface is used by the operating system to automatically load an operating system from a pre-boot operating environment.

UEFI is a personal computer system specification that defines the software interface between the operating system and system firmware as an alternative to BIOS. The extensible firmware interface is responsible for power-on self-test (POST), contacting the operating system, and providing an interface between the operating system and the hardware.

UEFI was formerly the Intel Boot Initiative developed by Intel in 1998 and was later renamed Extensible Firmware Interface (EFI). Intel handed it over to the Unified Extensible Firmware Interface Forum (Unified EFI Forum) for promotion and development in 2005. To highlight this, EFI was also renamed UEFI (Unified EFI). The founders of the UEFI Forum are 11 well-known computer companies, including hardware manufacturers such as Intel and IBM, software manufacturer Microsoft, and BIOS manufacturers AMI, Insyde and Phoenix.

The Extensible Firmware Interface (EFI) was originally developed by Intel. In December 2002, Intel released its specified version-version 1.1. After that, Intel no longer released other EFI specification formats. Regarding the EFI specification, Intel handed over this specification format to the UEFI Forum for promotion and development in 2005, and later changed the name to Unified EFI (UEFI). The UEFI Forum released version 2.1 of the specifications on January 7, 2007, which added and improved cryptography, network authentication, and user interface architecture compared to version 1.1.

Composition of Unified Extensible Firmware Interface (UEFI)

It is generally believed that UEFI consists of the following parts:

• Pre-EFI initialization module

• EFI driver execution environment

• EFI driver

• Compatibility Support Module (CSM)

• EFI high-level application

• GUID disk partition table

In implementation, the Unified Extensible Firmware Interface (UEFI) initialization module and driver execution environment are usually integrated in a read-only memory. The Pre-EFI initialization program is first executed when the system is booted. It is responsible for the initial initialization of the CPU, chipset and memory, and then loads the EFI driver execution environment (DXE). When DXE is loaded and running, the system has the ability to enumerate and load other EFI drivers.

In a system based on PCI architecture, the EFI drivers of each PCI bridge and PCI adapter will be loaded and initialized one after another; at this time, the system will then enumerate and load the various buses behind each bridge and adapter and the device's EFI driver, and the cycle starts again until the last device's EFI driver is successfully loaded.

Because of this, the EFI driver can be placed anywhere on the system, as long as it can be correctly enumerated in order.

For example, for a RAID storage adapter with a PCI-E bus interface, its EFI driver will generally be placed in the extended read-only memory (PCI Expansion ROM) of this device that matches the PCI specification. When the PCI bus driver After being loaded and starting to enumerate its child devices, the storage adapter is correctly recognized and its EFI driver is loaded.

Some EFI drivers can also be placed in the EFI system partition (ESP) of a disk, as long as these drivers are not necessary components of the driver used to load the disk.

In the EFI specification, a GUID disk partition system (GPT) was introduced that broke through the limitations of the traditional MBR disk partition structure. In the new structure, the number of primary partitions on the disk is no longer limited (under the MBR structure, Only 4 primary partitions can exist). In addition, the combination of EFI/UEFI GUID can also support hard drives above 2.1 TB (tests show that 3TB hard drives using MBR and installing Windows 6.x 64-bit systems can only recognize 2.1 TB). And the partition type will be represented by GUID.

Among the many partition types, the EFI system partition can be accessed by UEFI firmware and can be used to store the operating system's boot program, EFI applications and EFI drivers.

The EFI system partition uses the FAT file system and has a small capacity. Under the Windows operating system, it is hidden by default. UEFI firmware boots the operating system by running the boot program in the EFI system partition.

CSM is a special module in the x86 platform UEFI system. It will provide similar functionality for operating systems that do not have UEFI boot capabilities (such as Windows XP) and 16-bit traditional Option ROMs (that is, non-EFI Option ROMs). System services based on traditional BIOS.

Secure Boot and CSM are not compatible, so before turning on CSM in the UEFI firmware settings, you need to turn off Secure Boot in the UEFI firmware settings.

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