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What is uefi bios of a motherboard. What is BIOS and UEFI. How to boot a computer

Many of us are increasingly encountering the standard UEFI Boot, which replaced the classic BIOS. At the same time, many would like to know better about UEFI Boot, but somehow they still don’t find the time or desire for this. In this material, I will try to eliminate the “blank spot” in the readers’ knowledge and tell you in detail what UEFI Boot is, describe its features and functionality.

There was a time when all computers were equipped with a BIOS built into the motherboard, which was a set of microprograms for testing the performance of the equipment, provided an API and supported booting the system. It was traditionally used in IBM-compatible machines and for the time being it performed its functions reliably, limited to 16-bit processes and 1-MB addressing.

With the development of technology, the “good old” BIOS no longer meets modern requirements, it turned out to be insufficiently flexible and modern, and it was replaced by its successor - UEFI Boot, which supports almost all standards of modern equipment.

UEFI(Unified Extensible Firmware Interface) dates back to 2003, when Intel created a BIOS replacement for its 64-bit servers for Itanium microprocessors. At that time, this standard was called EFI (an abbreviation for Extensible Firmware Interface). Later, when it entered the Unified EFI Forum, this concept was named UEFI and continued its development as a unified IT industry standard, in the development of which the most famous computer hardware manufacturers take part.

It is known that UEFI Boot is, like its predecessor, a standard that is an interface connecting the operating system and firmware that perform low-level operation of connected equipment. Its purpose is to initialize the hardware and transfer control to the OS boot loader.

You can see what UEFI looks like and what it is in the video:

Advantages of UEFI over BIOS


Difference 1. Visual component

Many UEFI elements look like a traditional BIOS, but some have been changed beyond recognition. A more pleasing picture, convenient overclocking options, a convenient and accessible interface, and mouse support. The changes are undoubtedly pleasing to the eye.

Difference 2. 16 vs 32

While BIOS is limited to 16-bit processes and 1 megabyte memory addressing, UEFI has no such restrictions. It works in both 32 and 64-bit modes, allows you to work with significantly larger amounts of memory, and is little dependent on the computer architecture. The UEFI Boot specification provides drivers for system components regardless of what processor is used in your PC.

Difference 3. Working volumes

The MBR in the BIOS was limited to four main partitions on the disk, and the boot disks themselves had a maximum size of 2.2 terabytes. If previously this was quite enough, then the capabilities of today's drives already exceed the specified size. UEFI uses GUID partition markings, allowing booting from 9.4 ZB disks. For the uninitiated, I’ll explain that one zetabyte is 1024 times 1024 times 1024 gigabytes.

It is clear that this UEFI Boot allows you to work with a significantly larger size of boot options, it is not tied to any specific file system, and has fantastic network capabilities. The system boot loader can serve as an extension to UEFI, and the latter itself, if necessary, can itself perform the functions of a boot loader. At the same time, it is even possible to load the user’s own drivers into UEFI. Impressive, isn't it?

Difference 4. Extensions

UEFI supports both old extensions (for example, ACPI) and new ones based on EFI specifications with greater functionality (Asus Splashtop, etc.).

Difference 5. Easy control

Since most options are presented in the form of visual graphic symbols, working with them is simple and convenient. Try it and see for yourself.

Difference 6. Secure Boot

The UEFI standard has another advantage called Secure Boot– this is a special protection against the initialization of unsigned code, protecting the system from replacing the bootloader and launching unlicensed software. It was born in version UEFI 2.2, and is implemented in many modern computers. Despite its many advantages, users prefer to disable Secure Boot, since its disadvantages sometimes outweigh its advantages, especially when there is a need to boot the PC from a flash drive.

Conclusion

What is UEFI Boot? As you can see, the UEFI Boot specification has a number of serious advantages over its predecessor. A more convenient and accessible interface, improved operating speed, support for significantly larger amounts of memory and a system hard drive - this and much more makes UEFI the most effective and modern option. If you have a modern PC (circa 2011 onwards), maybe it's time to look into your UEFI and get to know it better.

  • Translation

Newer computers use UEFI firmware instead of the traditional BIOS. Both of these programs are examples of low-level software that runs when the computer starts, before the operating system boots. UEFI is a newer solution, it supports larger hard drives, boots faster, is more secure - and, very conveniently, has a graphical interface and mouse support.

Some newer computers that ship with UEFI still call it "BIOS" to avoid confusion for users accustomed to traditional PC BIOSes. But even if you see it mentioned, know that your new computer will most likely be equipped with UEFI, not BIOS.

What is BIOS?


BIOS stands for Basic Input-Output system, a basic input-output system. It is a low-level program stored on a chip on your computer's motherboard. The BIOS loads when you turn on your computer and is responsible for waking up its hardware components, making sure they are working correctly, and then launching the boot loader program, which starts the Windows operating system or any other operating system you have installed.

The BIOS setup screen allows you to change many settings. Computer hardware configuration, system time, boot order. This screen can be called up at the beginning of the computer boot by pressing a certain key - it is different on different computers, but the Esc, F2, F10, Delete keys are often used. By saving a setting, you store it in the motherboard memory. When you boot your computer, the BIOS will configure it as specified in the saved settings.

Before loading the operating system, the BIOS goes through POST, or Power-On Self Test, self-testing after switching on. It checks that the hardware is configured correctly and is working properly. If something is wrong, you will see a series of error messages on the screen or hear a mysterious squeak from the system unit. What exactly the sound signals mean is described in the computer instructions.

When the computer boots after POST, the BIOS looks for Master Boot Record, or MBR - master boot record. It is stored on the boot device and is used to launch the OS boot loader.

You may also have seen the acronym CMOS, which stands for Complementary Metal-Oxide-Semiconductor. It refers to the memory in which the BIOS stores various settings. Its use is obsolete, since this method has already been replaced by flash memory (also called EEPROM).

Why is the BIOS outdated?

BIOS has been around for a long time and has evolved little. Even MS-DOS computers released in the 1980s had a BIOS.

Of course, over time, the BIOS changed and improved. Its extensions were developed, in particular, ACPI, Advanced Configuration and Power Interface (advanced configuration and power management interface). This allowed the BIOS to more easily configure devices and more advanced power management, such as hibernation. But BIOS has not evolved as much as other computer technologies since MS-DOS.

The traditional BIOS still has serious limitations. It can only boot from hard drives with a capacity of no more than 2.1 TB. Nowadays, 3 TB disks are ubiquitous, and a computer with BIOS will not boot from them. This is a BIOS MBR limitation.

The BIOS must operate in 16-bit processor mode and only 1 MB of memory is available to it. It has trouble initializing multiple devices at the same time, resulting in a slow boot process during which all hardware interfaces and devices are initialized.

The BIOS was long overdue for replacement. Intel began working on the Extensible Firmware Interface (EFI) back in 1998. Apple chose EFI when it switched to Intel architecture on its Macs in 2006, but other manufacturers didn't follow suit.

In 2007, Intel, AMD, Microsoft and PC manufacturers agreed on a new specification, the Unified Extensible Firmware Interface (UEFI), a unified extensible firmware interface. This is an industry standard maintained by the UEFI forum and does not depend solely on Intel. UEFI support in Windows was introduced with the release of Windows Vista Service Pack 1 and Windows 7. Most computers you can buy today use UEFI instead of BIOS.

How UEFI replaces and improves BIOS


UEFI replaces the traditional BIOS on PCs. There is no way to change the BIOS to UEFI on an existing PC. You need to buy hardware that supports UEFI. Most versions of UEFI support BIOS emulation so you can install and run a legacy OS that expects a BIOS instead of UEFI - so they are backwards compatible.

The new standard bypasses BIOS limitations. UEFI firmware can boot from drives larger than 2.2 TB - the theoretical limit for them is 9.4 zettabytes. This is approximately three times the amount of data contained on the Internet today. UEFI supports such volumes due to the use of GPT partitioning instead of MBR. It also has a standardized boot process and runs EFI executable programs instead of code located in the MBR.

UEFI can operate in 32-bit or 64-bit modes and its address space is larger than that of the BIOS - which means faster booting. This also means that UEFI setup screens can be made more beautiful than those of the BIOS, including graphics and mouse support. But this is optional. Many computers to this day run UEFI with text mode, which look and work just like the old BIOS screens.

There are many other features built into UEFI. It supports Secure Boot, in which you can verify that the OS boot has not been modified by any malicious program. It can support network operation, which allows for remote configuration and debugging. With a traditional BIOS, you had to sit directly in front of the computer to set up your computer.

And this is not just a BIOS replacement. UEFI is a small operating system that runs on top of the PC's firmware, so it can do much more than BIOS. It can be stored in flash memory on the motherboard or loaded from a hard drive or network.

Different computers have different interfaces and UEFI properties. It all depends on the computer manufacturer, but the basic capabilities are the same for everyone.

How to Access UEFI Settings on a Modern PC

If you are a regular user, you will not notice the transition to a computer with UEFI. The computer will boot and shut down faster, and you will also have access to disks larger than 2.2 TB.

But the procedure for accessing the settings will be slightly different. To access the UEFI settings screen, you may need to use the Windows boot menu. PC manufacturers didn't want to slow down a fast booting computer by waiting for a key to be pressed. But we also came across UEFIs in which manufacturers left the ability to enter the settings in the same way as in the BIOS - by pressing a key during boot.

UEFI is a big update, but it happened quietly. Most PC users won't notice it and don't have to worry about their new computer using UEFI instead of the regular BIOS. PCs will simply perform better and support more modern hardware and features.

For a more detailed explanation of the differences in the UEFI boot process, see

BIOS is a well-known term among computer owners that has been used for many years. In the fall of 2017, Intel announced its plans to completely abandon BIOS on all of its platforms by 2020. Instead of BIOS it will now be used only UEFI, which may lead many to a logical question: why is UEFI better than BIOS and what is the difference between them?

BIOS chip on a Gigabyte motherboard.

UEFI and BIOS belong to the category of so-called “low-level” software, which starts even before the computer starts loading the operating system. UEFI is a more modern solution and it supports a large number of convenient features that are useful on modern computers. It often happens that manufacturers call UEFI on their computers with the traditional word “BIOS” so as not to confuse the user. Still, there is a big difference between UEFI and BIOS, and modern computers are mostly equipped with UEFI.

What is BIOS

BIOS is short for “ BasicInput-OutSystem" or " basic input/output system". It lives on a special chip inside the motherboard (pictured above) and does not depend on whether a hard drive is installed in the computer. When you turn on your computer, the first thing that turns on is the BIOS. This system is responsible for “waking up” the hardware components of your computer, checking their normal functioning, activating the bootloader and then starting the operating system.

BIOS as old as time.

The user can configure a large number of different parameters within the BIOS. Component configuration, system time, boot order, and so on. You can enter the BIOS using a special key when turning on the PC. It may be different for different computers. For example, Esc, F2, F10 or Delete. The manufacturer himself decides which one to choose. After changing the settings, all parameters are written to the motherboard itself.

The BIOS is also responsible for a process called POST – “ Power-OnSelf-Test” or " power-on check". POST checks the suitability of the computer configuration and the health of the hardware components. If something goes wrong, a corresponding error is displayed on the screen or the computer begins to make a number of certain sounds (there is also the concept of POST codes, and some motherboards even have a corresponding display installed to display them). The intensity of these sounds depends on the type of error, and in order to decipher them, you need to refer to the manufacturer’s website or the user manual.

After POST completes, the BIOS looks for the Master Boot Record (MBR) that is stored on the computer's storage media. Then the bootloader is initialized and the operating system starts. BIOS also often uses the term CMOS, which stands for " ComplementaryMetal-OxideSemiconductor" or " auxiliary metal oxide semiconductor". This is a designation for special memory that is powered by a battery built into the motherboard. The memory stores various BIOS settings and it is often recommended to remove the battery from the motherboard to reset the BIOS settings. In modern computers, CMOS has been replaced by flash memory (EEPROM).

Why is the BIOS outdated?

BIOS is a very old system that existed back in 1980 (and was developed even earlier), at the time of the launch of MS-DOS. Of course, over time, the BIOS has developed and improved, but the concept and basic operating principles have remained the same. The development of BIOS is virtually zero when compared with the development of computers and technology in general.

Traditional BIOS has many serious limitations. For example, it can start the system only from a partition no larger than 2.1 TB (maximum 4 partitions) or less. In modern realities, users buy very capacious drives, the volume of which often exceeds 4 and even 8 TB. The BIOS will not be able to work with such media. This is due to the way the MBR works (the master boot record uses 32-bit elements). In addition, the BIOS operates in 16-bit mode (as it was developed back in the 70s) and has only 1 MB of addressable space for operation. The BIOS also has problems initializing a large number of components at once, which leads to a slow start of the computer.

The BIOS has been in need of replacement for a long period of time. Intel began developing EFI (Extensible Firmware Interface) back in 1998, and Apple switched to EFI in 2006, when the transition to Intel architecture took place. In 2007, Intel, AMD, Microsoft and various computer manufacturers approved the UEFI specification - " Unified Extensible Firmware Interface" or " unified extensible firmware interface". Windows gained UEFI support in Windows Vista SP1 and Windows 7. Today, almost all computers use UEFI instead of BIOS.

Why UEFI is better than BIOS

UEFI is installed instead of BIOS on various PCs that you can find in electronics stores. It should be noted right away that the user cannot switch from BIOS to UEFI on existing hardware. To do this, you need to purchase new hardware that supports UEFI. The vast majority of UEFI computers include BIOS emulation (often called Legacy BIOS) to allow the user to install and boot an older operating system that requires the BIOS to run. In other words, UEFI is backwards compatible.

A much more modern and user-friendly UEFI interface.

The new standard got rid of the unpleasant BIOS restrictions. A computer with UEFI can boot from drives larger than 2.2 TB. Theoretically, the maximum storage capacity for UEFI is 9.4 Tb (9.4 trillion gigabytes). That's a lot. The whole point is that UEFI uses the GPT scheme with 64-bit elements..

UEFI runs in 32 and 64 bit modes and also has more memory to work with. This, in turn, translates into faster processor load and ease of use. UEFI systems often have beautiful interfaces that support mouse input (in the screenshot above). There are also a number of other advantages. For example, UEFI supports Secure Boot. This is a special procedure that checks the operating system being loaded and makes sure that no malicious or third-party software will interfere during its loading. UEFI also has support for various network functions, which is useful when solving technical problems with your computer. In a traditional BIOS, the user must have physical access to the computer, whereas in UEFI there is a remote access option for configuration.

In general, UEFI is such a small operating system. It can be stored on the flash memory of the motherboard or it can be loaded from a hard/network drive. Different computers with different UEFIs have equally different interfaces and capabilities. It all depends on the preferences of your computer manufacturer.

UEFI was a big upgrade for modern computers, but the vast majority of users are unlikely to notice any significant difference. And many people are not interested in this question at all. Still, we must understand that the advent of UEFI instead of BIOS has become an extremely positive evolutionary change in the world of modern computers, even if all its charms and innovations remain hidden deep in the computer’s motherboard. Now the industry is still in a transition state from BIOS to UEFI, so all the delights of the new standard will be revealed in the near future. To speed up this process, Intel has decided to completely abandon the BIOS until 2020, and that's a good thing.

EFI(E xtensible F irmware I interface)— interface for centralizing equipment at the moment the system is turned on. Regulates the processes occurring between the operating system and firmware that manage low-level hardware functions. EFI boots the computer and subsequently transfers control to the operating system bootloader. It is a logical replacement for the BIOS interface, traditionally used by IBM PC-compatible computers.

Intel developed the first EFI specification. Later, the interface changed its name: the latest version of the standard is called UEFI (U unified E xtensible F irmware I interface). Today, the UEFI standard is being developed by the Unified EFI Forum association.

The EFI standard has support for graphical menus, as well as some additional features (for example, Aptio or Great Wall UEFI).

Story

Originally, the EFI standard was intended for use in the first Intel-HP Itanium systems, which appeared in the mid-90s. The limited capabilities that PC-BIOS demonstrated (16-bit code, 1 MB addressable memory, IBM PC/AT hardware limitations, etc.) were unacceptable for use on large server platforms, and Itanium was planned precisely for such.

It is noteworthy that EFI was originally called Intel Boot Initiative, it was later renamed.

Specifications

The history of the EFI standard began with the release of version 1.01, but it did not see widespread use as it was quickly withdrawn from the market due to legal problems related to the use of the trademark.

Later, on December 1, 2002, EFI version 1.10 was introduced, which included the EFI driver model, as well as several “cosmetic” improvements over version 1.02.

In 2005, Intel assigned the EFI specification to the UEFI Forum, which subsequently became responsible for further development of the interface. At the same time, the EFI standard was renamed Unified EFI (UEFI) in order to emphasize the change that had occurred. It is noteworthy that, despite the name change, both terms are still freely used in most documents.

On January 7, 2007, the UEFI Forum released UEFI version 2.1, which introduced improved cryptography, network authentication, and an updated user interface architecture.

The EFI interface contains tables that include a lot of different data: information about the platform, boot and runtime services available to the operating system boot loader and the operating system itself. Some BIOS extensions (ACPI or SMBIOS) are also included in EFI - they do not require a 16-bit runtime interface.

Services

EFI defines boot services that include support for:

  • text and graphic console;
  • blocks;
  • file services;

the interface also defines runtime services (date, time and memory).

Device Drivers

The EFI standard, in addition to standard, architecture-specific drivers, also defines a platform-independent driver environment. this environment is called EFI Byte Code(EBC). The UEFI specification requires system software to provide an interpreter for any EBC images loaded (actually or potentially) into the environment.

Thus, EBC can be easily correlated with the hardware-independent Open Firmware used in Apple Macintosh and Sun Microsystems SPARC computers.

Some architecture-specific types of EFI drivers can be equipped with interfaces for use by the operating system, which allows the operating system itself to use EFI as basic graphics and networking support before loading the drivers.

Download Manager

The EFI Boot Manager is used to select and then boot an operating system. Thus, the need for a specific boot algorithm is eliminated: the bootloader is an EFI application.

Disc support

In addition to the standard disk partitioning method (MBR), EFI has support for GUID Partition Table (GPT). This scheme is free of any MBR-specific restrictions. The EFI standard does not specify file systems, but EFI implementations typically support the FAT32 file system.

Shell

The standard's open shell environment allows the user to load it in order to perform certain operations. This is much more convenient: the user is spared from loading the operating system itself. The shell is a simple EFI application that can be stored in platform ROM (or on a separate device whose drivers are located in ROM).

In addition, the user can use the shell to run other EFI applications (for example, configuring or installing an operating system, or diagnosing, configuring, or updating firmware). The shell's functions also include playing CD/DVD media without loading the operating system. In addition, the EFI shell allows command-based operations to copy or move files and directories, provided that the work is performed on supported file systems. You can also download/unload drivers. And finally, the shell can use the full TCP/IP stack.

The EFI shell has support for scripts in the form of files with the extension .nsh (analogous to a batch file in DOS).

Command names are often borrowed from command line interpreters (COMMAND.COM or Unix shell). The EFI shell can fully act as an alternative and full-fledged analogue of the command line interpreter or the BIOS text interface.

Extensions

EFI extensions are loaded from almost any non-volatile storage device that is connected to the PC.


Implementation

Intel Platform Innovation Framework

The Intel Platform Innovation Framework (“Intel Innovation Toolkit”) is a set of specifications released by Intel in collaboration with EFI. In this case, EFI defines the interface between the operating system and the hardware and software, and the toolkit is responsible for defining the structure used to create the embedded software. This determination is made at a lower level than the functions provided in EFI.

For example, the toolkit includes all the steps that must be overcome to correctly initialize the computer from the moment it is turned on. These internal firmware capabilities are not part of the EFI specification, but are included in the UEFI Platform Initialization Specification. This toolkit has been tested on the XScale, Itanium and IA-32 platforms.

Compatibility with the operating system, in the case of the x86 platform, is achieved through the use of Compatibility Support Module(CSM), which contains a 16-bit program (CSM16), which is implemented by the BIOS manufacturer. It also includes a special layer, the functions of which include communication of the CSM16 with the tools.

Intel is the author of a unique implementation for the toolkit, codenamed “Tiano”. This is a complete embedded software implementation with EFI support. It lacks the traditional 16-bit part of the CSM, but it does provide the interfaces that are needed for add-ons implemented by BIOS manufacturers. Intel does not distribute the full implementation of Tiano to end users. Part of this implementation has been released as source code for the TianoCore project, like EFI Developer Kit(EDK). This implementation includes EFI and part of the hardware initialization code, but at the same time, it hides the characteristic features of the embedded software itself.

Products built on the EFI standard can be purchased through third-party BIOS manufacturers (for example, American Megatrends (AMI) and Insyde Software). Some implementations are completely based on Tiano, others comply with the specifications, but are not based on the Intel implementation.

Platforms using EFI; accompanying tools

In 2000, Intel developed systems built on the Itanium platform. They had EFI 1.02 support.

In 2002, Hewlett-Packard released systems built on the Itanium 2 platform. They supported EFI version 1.10, and were able to boot Windows, Linux, FreeBSD and HP-UX operating systems.

Itanium or Itanium 2 systems released with integrated EFI-compatible software are required to comply with the DIG64 specification.

In November 2003, Gateway unveiled the Gateway 610 Media Center, which was the first x86 system built on Windows. It used embedded software that was based on the toolkit, InsydeH2O from Insyde Software. BIOS support was provided through the Compatibility Support Module (CSM).

January 2006, Apple introduces its first Macintosh PCs built on the Intel platform. The systems use EFI and related tools, instead of Open Firmware, which was used on previous PowerPC platform systems.

On April 5, 2006, Apple introduced Boot Camp, a standard package that allows you to create a disk with Windows XP drivers. In addition, the new package contained a disk partitioning tool that allows you to install Windows XP while leaving the current Mac OS X operational. In addition, a firmware update was released. It added BIOS support for EFI implementation. Subsequent lines of Macintosh computer models were released with updated and built-in software. So, today, all Macintosh computers have the ability to load BIOS-compatible operating systems.

Branded "Intel" motherboards are produced mainly with embedded software built on the basis of tools (for example, DP35DP). Thus, in 2005, over 1 million Intel systems were produced. Production of new cell phones, desktop PCs and servers running on the toolkit started in 2006. For example, all motherboards built on the Intel 945 system logic set use tools in their work. However, embedded software, as a rule, does not include EFI support; it is limited only to BIOS support.

Since 2005, the EFI standard has been introduced into non-PC architectures (for example, embedded systems built on XScale). The EDK includes a separate NT32 target that allows EFI software and its applications to be embedded in Windows applications. In 2007, Hewlett-Packard introduced the 8000 series printer. It was the first printer to include EFI-compatible embedded software. In 2008, MSI introduced a line of motherboards built on the Intel P45 chipset; they had EFI support.

OS

  • Since the 2000s, GNU/Linux operating systems have often used EFI to boot.
  • Since 2002, HP-UX operating systems began to use EFI as a boot mechanism in systems built on the IA-64 platform. OpenVMS operating systems have used the standard since early 2005.
  • Apple adopted the EFI standard by releasing a line of computers built on Intel architecture. Mac OS X 10.4 (Tiger) for Intel and Mac OS X 10.5 (Leopard) had support for EFI v1.10 not only in 32-bit mode, but also on 64-bit CPUs. Thus, using the EFI boot loader, installing Microsoft Windows 7 on Apple computers remained impossible, since this operating system requires UEFI or an even newer version.
  • Microsoft Windows has EFI support for 64-bit architectures. Microsoft notes that the lack of EFI support on 32-bit CPUs is due to lack of input from PC manufacturers. Microsoft's migration to 64-bit operating systems does not allow the use of EFI 1.10 because 64-bit extensions are not supported by the processor environment. x86-64 support is included in UEFI 2.0. Itanium versions of Windows 2000 (Advanced Server Limited Edition and Datacenter Server Limited Edition) have support for EFI 1.1. Windows Server 2003 for IA-64, 64-bit versions of Windows XP and Windows 2000 Advanced Server Limited Edition, tailored specifically for the Intel Itanium processor family, have EFI support, defined for this platform by the DIG64 specification. Microsoft developers have introduced UEFI support in 64-bit Windows operating systems starting with Windows Server 2008 and Windows Vista Service Pack 1.

Flaws

The EFI standard has come under deafening criticism for adding complexity to the system. Many experts noted that EFI does not provide the operating system with key advantages, but at the same time significantly complicates it. In addition, alternative BIOS implementations that are completely open source (OpenBIOS and coreboot) have been abandoned in favor of EFI.

In September 2011, Microsoft announced that the certification of Microsoft Windows 8 compatible computers could lead to the subsequent production of devices that, under no circumstances, would support any other operating system. Microsoft has clarified that vendors may be able to add other signatures. A little later this was made a mandatory certification requirement. However, as for devices on ARM, in their case the requirement is the following: completely disable the “secure boot” function. In this case, installing other operating systems also ceases to be possible.

Many users believe that the computer boots using the operating system, but in fact this is only partly true. In this material, you will learn how a PC actually boots and become familiar with such important concepts as BIOS, CMOS, UEFI and others.

Introduction

For many people, working with a computer begins after loading the operating system. And this is not surprising, since the vast majority of the time, modern PCs are actually used using the convenient graphical shell of Windows or any other OS. In this friendly environment for us, we not only launch programs, applications or games, but also carry out settings, as well as configure system parameters to suit our own needs.

But, despite all its multifunctionality, the operating system cannot do everything, and in some key moments, it is simply powerless. In particular, this applies to the initial boot of the computer, which occurs completely without her participation. Moreover, the launch of the OS itself largely depends on the success of this procedure, which may not occur if problems arise.

This may be news to some, but in reality, Windows is not responsible for booting the computer from start to finish; it only continues it at a certain stage and finishes it. The key player here is a completely different firmware - the BIOS, the purpose and main functions of which we will talk about in this material.

What is BIOS and why is it needed?

The key components of any computer device are a combination of processor and RAM, and this is not without reason. The processor is rightly called the heart and brain of any PC, since all the main mathematical operations are entrusted to it. In this case, the CPU can only take all commands and data for calculations from RAM. He also sends the results of his work there. The processor does not directly interact with any other information storage, for example, hard drives.

This is where the main problem lies. In order for the processor to begin executing operating system commands, they must be in RAM. But when the PC is turned on, the RAM is empty, since it is volatile and cannot store information when the computer is turned off. At the same time, by themselves, without the participation of the system, computer devices cannot place the necessary data in memory. And here we are faced with a paradoxical situation. It turns out that in order to load the OS into memory, the operating system must already be in RAM.

To resolve this situation, at the dawn of the era of personal computers, IBM engineers proposed using a special small program called the BIOS, sometimes called the boot loader.

Word BIOS(BIOS) is an abbreviation for four English words Basic Input/Output System, which translated into Russian means: “Basic input/output system.” This name was given to a set of firmware responsible for the operation of the basic functions of video adapters, displays, disk drives, drives, keyboards, mice and other basic input/output devices.

The main functions of the BIOS are the initial startup of the PC, testing and initial configuration of the equipment, distribution of resources between devices and activation of the operating system boot procedure.

Where is the BIOS stored and what is CMOS

Considering that the BIOS is responsible for the very initial stage of booting the computer, regardless of its configuration, this program should be available for basic devices immediately after pressing the PC power button. That is why it is not stored on the hard drive, like most ordinary applications, but is written to a special flash memory chip located on the motherboard. Thus, access to the BIOS and starting the computer is possible even if no storage media is connected to the PC at all.

The very first computers used read-only memory chips (ROM or ROM) to store the BIOS, onto which the program code itself was written once at the factory. Somewhat later, they began to use EPROM and EEROM chips, in which it was possible, if necessary, to rewrite the BIOS, but only with the help of special equipment.

In modern personal computers, the BIOS is stored in chips based on flash memory, which can be rewritten using special programs directly on the PC at home. This procedure is usually called flashing and is required to update the firmware to new versions or replace it in case of damage.

Many BIOS chips are not soldered onto the motherboard, like all other components, but are installed in a special small connector, which allows you to replace it at any time. True, this feature is unlikely to be useful to you, since cases requiring replacement of the BIOS chip are very rare and practically never occur among home users.

Flash memory for BIOS storage can have different capacities. In previous times, this volume was very small and amounted to no more than 512 KB. Modern versions of the program have become somewhat larger and have a volume of several megabytes. But in any case, compared to modern applications and multimedia files, this is simply minuscule.

In some advanced motherboards, manufacturers can install not one, but two BIOS chips at once - a main one and a backup one. In this case, if something happens to the main chip, the computer will boot from the backup one.

In addition to the flash memory in which the BIOS itself is stored, there is another type of memory on the motherboard that is designed to store configuration settings for this program. It is manufactured using a complementary metal oxide semiconductor or CMOS(Complementary Metal Oxide Semiconductor). This abbreviation is the name given to specialized memory that contains computer startup data used by the BIOS.

CMOS memory is powered by a battery installed on the motherboard. Thanks to this, when you disconnect the computer from the outlet, all BIOS settings are saved. On older computers, CMOS memory functions were assigned to a separate chip. In modern PCs it is part of the chipset.

POST procedure and initial PC boot

Now let's see what the initial process of booting a computer looks like and what role the BIOS plays in it.

After pressing the computer's power button, the power supply starts up first, starting to supply voltage to the motherboard. If it is normal, then the chipset gives a command to reset the internal memory of the central processor and start it up. After this, the processor begins to sequentially read and execute commands written in system memory, the role of which is played by the BIOS chip.

At the very beginning, the processor receives a command to perform self-testing of computer components ( POST- Power-On Self-Test). The POST procedure includes several stages, most of which you can watch on the PC screen immediately after turning it on. The sequence of events before the operating system starts loading is as follows:

1. First, the main system devices are determined.

3. The third step is setting up the system logic set, or more simply, the chipset.

4. Then the video card is searched and identified. If an external (independent) video adapter is installed in the computer, then it will have its own BIOS, which the main system BIOS will look for in a certain range of memory addresses. If an external graphics adapter is found, the first thing you will see on the screen will be an image with the name of the video card generated by its BIOS.

5. After finding the graphics adapter, the integrity of the BIOS parameters and battery status begins to be checked. At this moment, those same mysterious white inscriptions begin to appear on the monitor screen one after another, causing trepidation in inexperienced users due to a lack of understanding of what is happening. But in fact, nothing supernatural happens at this moment, as you will now see for yourself. The first, topmost inscription, as a rule, contains the logo of the BIOS developers and information about its installed version.

6. Then testing of the central processor starts, after which data about the installed chip is displayed: the name of the manufacturer, model and its clock frequency.

7. Next, testing of RAM begins. If everything goes well, the total installed amount of RAM is displayed on the screen with the inscription OK.

8. Upon completion of checking the main components of the PC, the search for the keyboard and testing of other input/output ports begins. In some cases, the computer may stop booting at this stage if the system is unable to detect the connected keyboard. In this case, a warning about this will immediately be displayed on the screen.

9. Next, the detection of storage devices connected to the computer begins, including optical drives, hard drives and flash drives. Information about the found devices is displayed on the screen. If several controllers from different manufacturers are installed on the motherboard, their initialization procedure can be displayed on different screens.

Controller Definition ScreenSerialATA, which has its ownBIOS, with the output of all devices connected to it.

10. At the final stage, resources are distributed between the found internal PC devices. In older computers, after this a summary table with all detected equipment is displayed. In modern machines the table is no longer displayed on the display.

11. Finally, if the POST procedure is successful, the BIOS begins searching the connected drives Main Boot Area(MBR), which contains data about the operating system startup and the boot device to which further control must be transferred.

Depending on the BIOS version installed on the computer, the POST procedure may take place with slight changes from the order described above, but in general, all the main steps that we have indicated will be performed when booting each PC.

BIOS Setup Utility

BIOS is a configurable system and has its own program for setting up some PC hardware parameters, called BIOS Setup Utility or CMOS Setup Utility. It is called by pressing a special key during the POST self-test procedure. On desktop computers, the Del key is most often used for this purpose, and on laptops F2.

The graphical interface of the hardware configuration utility is very ascetic and has remained virtually unchanged since the 80s. All settings here are made only using the keyboard - mouse operation is not provided.

CMOS/BIOS Setup has a lot of settings, but the most popular ones that the average user may need include: setting the system time and date, choosing the order of boot devices, enabling/disabling additional equipment built into the motherboard (sound, video or network adapters) , controlling the cooling system and monitoring the processor temperature, as well as changing the system bus frequency (overclocking).

For different motherboard models, the number of configurable BIOS parameters can vary greatly. The widest range of settings is usually available on expensive desktop motherboards aimed at enthusiasts, fans of computer games and overclocking. The most meager arsenal, as a rule, is found in budget boards designed for installation in office computers. The vast majority of mobile devices also lack a variety of BIOS settings. We will talk in more detail about the various BIOS settings and their impact on the operation of the computer in a separate article.

BIOS development and update

As a rule, for almost every motherboard model, its own BIOS version is developed, which takes into account its individual technical features: the type of chipset used and the types of soldered peripheral equipment.

BIOS development can be divided into two stages. First, a basic version of the firmware is created, which implements all functions, regardless of the chipset model. Today, the development of such versions is mainly carried out by American Megatrends (AMIBIOS) and Phoenix Technologies, which in 1998 absorbed the then major player in this market - Award Software (AwardBIOS, Award Modular BIOS, Award WorkstationBIOS).

At the second stage, motherboard manufacturers are involved in the development of BIOS. At this point, the basic version is modified and improved for each specific board model, taking into account its features. At the same time, after the motherboard enters the market, work on its BIOS version does not stop. Developers regularly release updates that can fix found errors, add support for new hardware, and expand the functionality of the program. In some cases, updating the BIOS allows you to breathe new life into a seemingly outdated motherboard, for example, adding support for a new generation of processors.

What is UEFI BIOS

The basic principles of operation of the system BIOS for desktop computers were formed in the distant 80s of the last century. Over the past decades, the computer industry has developed rapidly, and during this time situations have constantly arisen when new device models turn out to be incompatible with certain BIOS versions. To solve these problems, developers constantly had to modify the code of the underlying input/output system, but in the end a number of software limitations have remained unchanged since the days of the first home PCs. This situation led to the fact that the BIOS in its classic version finally ceased to meet the requirements of modern computer hardware, preventing its distribution in the mass sector of personal computers. It became clear that something needed to change.

In 2011, with the launch of motherboards for Intel Sandy Bridge generation processors installed in the LGA1155 socket, the mass introduction of a new software interface for booting a computer began - UEFI.

In fact, the first version of this alternative to the regular BIOS was developed and successfully used by Intel in server systems back in the late 90s. Then, the new interface for booting a PC was called EFI (Extensible Firmware Interface), but already in 2005 its new specification was called UEFI (Unified Extensible Firmware Interface). Today, these two abbreviations are considered synonymous.

As you can see, motherboard manufacturers were in no particular hurry to switch to the new standard, trying to improve traditional BIOS variations until the last minute. But the obvious backwardness of this system, including its 16-bit interface, the inability to use more than 1 MB of memory address space, the lack of support for drives larger than 2 TB and other constant insoluble compatibility problems with new equipment nevertheless became a serious argument for switching to a new software solution .

What changes did the new boot interface proposed by Intel bring with it and how does it differ from the BIOS? As with BIOS, the main task of UEFI is to correctly detect the hardware immediately after turning on the PC and transfer control of the computer to the operating system. But at the same time, the changes in UEFI are so profound that it would be simply incorrect to compare it with BIOS.

BIOS is a virtually unchangeable program code embedded in a special chip and interacts directly with computer hardware using its own software. The procedure for booting a computer using BIOS is simple: immediately after turning on the computer, it checks the hardware and loads simple universal drivers for the main hardware components. After this, the BIOS finds the operating system bootloader and activates it. Next, the OS loads.

The UEFI system can be called a layer between the computer's hardware components, with their own firmware, and the operating system, which allows it to also perform BIOS functions. But unlike BIOS, UEFI is a modular programmable interface that includes test, work and boot services, device drivers, communication protocols, functional extensions and its own graphical shell, which makes it look like a very lightweight operating system. At the same time, the user interface in UEFI is modern, supports mouse control and can be localized into several languages, including Russian.

An important advantage of EFI is its cross-platform and independence from the processor architecture. The specifications of this system allow it to work with almost any combination of chips, be it x86 architecture (Intel, AMD) or ARM. Moreover, UEFI has direct access to all computer hardware and platform-independent drivers, which makes it possible to organize, for example, Internet access or disk backup without starting the OS.

Unlike BIOS, the UEFI code and all its service information can be stored not only in a special chip, but also on partitions of both internal and external hard drives, as well as network storage. In turn, the fact that boot data can be placed on capacious drives makes it possible to provide EFI with rich functionality due to its modular architecture. For example, these could be developed diagnostic tools, or useful utilities that can be used both at the initial PC boot stage and after the OS starts.

Another key feature of UEFI is the ability to work with huge hard drives, partitioned using the GPT (Guid Partition Table) standard. The latter is not supported by any BIOS modification, since it has 64-bit sector addresses.

Booting a UEFI-based PC, as in the case of BIOS, begins with initializing the devices. But at the same time, this procedure is much faster, since UEFI can detect several components at once in parallel mode (BIOS initializes all devices in turn). Then, the UEFI system itself is loaded, under the control of which any set of necessary actions is performed (loading drivers, initializing the boot drive, starting boot services, etc.), and only after that the operating system is launched.

It may seem that such a multi-step procedure should increase the overall boot time of the PC, but in fact the opposite happens. With UEFI, the system starts much faster, thanks to built-in drivers and its own bootloader. As a result, before starting, the OS receives comprehensive information about the computer’s hardware, which allows it to start within a few seconds.

Despite all the progressiveness of UEFI, there are still a number of restrictions that hinder the active development and distribution of this bootloader. The fact is that to implement all the capabilities of the new boot interface, it requires full support from operating systems. To date, only Windows 8 allows you to fully use the capabilities of UEFI. Limited support for the new interface is available for 64-bit versions of Windows 7, Vista and Linux with kernel 3.2 and higher. UEFI capabilities are also used in the BootCamp boot manager by Apple in its own Mac OS X systems.

Well, how does a computer boot from UEFI if it uses an unsupported operating system (WindowsXP, 32-bit Windows 7) or file partitioning (MBR)? For such cases, the new boot interface has built-in Compatibility support module(Compatibility Support Module), which is essentially a traditional BIOS. This is why you can see many modern computers equipped with UEFI motherboards booting in the traditional way in BIOS emulation mode. Most often this happens because their owners continue to use HDD partitions with traditional MBR and do not want to switch to GPT partitioning.

Conclusion

It's clear that, unlike a traditional BIOS, UEFI is capable of much more than just the boot process. The ability to launch working services and applications, both at the initial stage of PC boot and after the operating system starts, opens up a wide range of new opportunities for both developers and end users.

But at the same time, it is still premature to talk about a complete abandonment of the basic input/output system in the near future. First of all, you need to remember that until now most computers are running WindowsXP and 32-bit Windows 7, which are not supported by UEFI. And hard drives partitioned according to the GPT standard can mostly be found only in new models of laptops based on Windows 8.

So as long as the majority of users, due to their habits or some other reasons, are tied to old versions of the OS and traditional methods of partitioning hard drives, BIOS will remain the main system for booting a computer.