Lis chaque section en anglais. Le resume en francais ("En bref") est juste un filet de securite : essaie de comprendre en anglais d'abord.
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This chapter is about configuration: using the system BIOS/UEFI Setup program, and configuring adapters you install. The Setup program lets you configure the motherboard, power settings, and devices, and adjust BIOS/UEFI-level performance settings.
The basic input/output system (BIOS) is an important motherboard component. It is commonly soldered directly onto the motherboard. BIOS is also known as the Unified Extensible Firmware Interface (UEFI), or simply EFI, BIOS/UEFI, or UEFI/BIOS.
BIOS generically has these functions: it holds and executes POST (power-on self-test) - a program that identifies, tests, and initializes basic hardware components; it holds a bootstrap program that finds an operating system and launches it, then lets the operating system take control; it holds Setup, a program for viewing and changing settings related to the display, date/time, processor, memory, and drives (Setup is also called BIOS/UEFI Setup, System Setup, or CMOS Setup); and it can optionally hand control to an adapter's own onboard BIOS so that card can initialize during boot.
POST runs during a cold boot (powering the computer on from off). A sign that POST is running is that the keyboard's indicator lights flash briefly. A warm boot (restarting a computer that is already on) does NOT run POST.
BIOS can be configured to check fewer devices during POST, which reduces boot time.
There are two main ways to configure a system or an adapter: through the Setup program held in system BIOS, or through the operating system.
If nothing appears on the screen when you try to enter Setup, and the display has power and a good cable connection, check the motherboard for LEDs (CPU, RAM, display/VGA, boot, etc.) - a lit LED can point to what is failing. Check the CPU, CPU fan, and RAM installation.
Run POST, hold the bootstrap program to find/launch the OS, hold the Setup program, and optionally hand control to an adapter's onboard BIOS.
No - only a cold boot runs POST.
Through the BIOS/UEFI Setup program, or through the operating system.
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Flash BIOS lets you upgrade (or downgrade) the BIOS without physically installing a new chip. Common BIOS/UEFI manufacturers include AMI (American Megatrends, Inc.), Phoenix Technologies, Byosoft, and Insyde Software; big PC makers like Dell, HP, and ASUS often customize their own BIOS chips or contract a BIOS manufacturer to customize one for them.
To find the current BIOS version: watch the screen while the computer boots (you can sometimes press Pause/Break to freeze the screen), enter BIOS Setup with the right keystroke during boot, or check it from within Windows. In Windows 10/11: Settings > Update & Security (Win10) / System (Win11) > Recovery > Advanced Startup 'Restart Now' > Troubleshoot > Advanced Options > UEFI Firmware Settings.
Upgrading the BIOS normally erases all BIOS software and settings stored in CMOS. Some manufacturers give you a utility to back up your current CMOS settings first. Before upgrading, if possible: back up your current CMOS settings, and back up your current BIOS file.
Unified Extensible Firmware Interface (UEFI) is a modern technology that bridges the operating system and the firmware. It can work alongside a traditional BIOS or replace it completely. Traditional BIOS always checked for certain things (like a keyboard) before allowing boot, which made configuring kiosks and touch-screen devices difficult - UEFI removes that limitation and gives a more flexible, customizable boot process.
Computers have Setup software built into the BIOS/UEFI chip, reached with specific keystrokes during boot (Esc, Insert, Del, F1, F2, F10, or a key combination like Ctrl+Alt+something), which vary by BIOS manufacturer. Most computers show which key(s) to press somewhere on screen during boot, usually in a corner. From Windows, you can check the System Information tool and look at 'BIOS Mode' to see if the computer is running UEFI mode or legacy (BIOS) mode.
With UEFI, unlike plain BIOS, you can use a mouse, possibly connect to the internet, run applications, run a virus scan, use a graphical interface (GUI), run utilities, or do a backup/restore - many more options in an easier environment.
Reasons most manufacturers moved to UEFI: it is a graphical, mouse-supported environment; it enables a virus scanner that is not tied to the operating system; it offers more than just configuration screens; it can offer optional internet access for troubleshooting/downloads; it gives better support for cooling, voltage levels, performance, and security; it supports larger hard drive capacities and drive partitioning not limited like traditional BIOS; it commonly shows temperature, voltage, CPU speed, bus speed, and fan speed data; and it can use a boot manager instead of relying only on a boot sector (see the GUID partition table / GPT, covered with storage devices).
The current CMOS settings and the current BIOS.
Any three of: mouse/GUI support, OS-independent virus scanning, optional internet access, better cooling/voltage/security support, support for larger drives and partitioning, a boot manager instead of only a boot sector.
Use the System Information tool and look at the 'BIOS Mode' field.
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BIOS/UEFI options vary by manufacturer, but many are similar across brands. You must always save your changes after making them - exiting without saving is a common mistake. Some manufacturers let you save screen captures of Setup screens to a USB flash drive.
Setup can also be used to disable connectors and ports built into the motherboard. For example, if a port fails, you can disable it in Setup and use a replacement adapter instead.
The key terms in the table below are all things the CompTIA A+ exam expects you to recognize.
| Setup option | Description |
|---|---|
| System information | Shows general info: processor, processor speed, RAM amount, type/number of hard drives and optical drives, BIOS/UEFI manufacturer, and BIOS/UEFI date. |
| General optimization | Speeds up booting by disabling things like memory checking, booting to the network, or booting from removable drives. |
| Boot options / Boot sequence / Boot drive order / Boot menu | Sets the order of devices the computer checks for an operating system. Change this when the system tries to boot from the wrong device. |
| CPU configuration / Advanced CPU settings | CPU TM function (throttles the CPU when overheated), clock speed (often not changeable), PECI (affects how thermal sensors report core temperature), Max CPUID (compatibility with older OSes), CPU Ratio Control (sets CPU multipliers), Vanderpool Technology (Intel virtualization). |
| Fan control / Fan considerations | Configures case and/or CPU fans, including silent mode or manual speed control. |
| Video options | Controls video memory, aperture size, and which video controller is primary/secondary. |
| Onboard device configuration | Modifies devices built into the motherboard: audio, Bluetooth, network, USB, or video ports. |
| Passwords: boot password, BIOS password, power on password, supervisor password, administrator password, or user password | Password-protects the BIOS/UEFI menu itself, so the computer can boot or so different access levels exist: a user password (minor changes like boot order or date/time) vs. a supervisor/administrator password (view and change ALL Setup options). Some vendors instead use levels: full access, limited access, view-only access, or no access. |
| Temperature monitoring / Hardware monitor | Shows CPU temperature and often motherboard temperature, voltages, clock speeds, and fan speeds. Check the cooling solution if temperature stays above 90degC. |
| Virus protection | Runs a small virus-scanning app built into BIOS/UEFI. Some OS or software updates require this to be disabled first. |
| Numlock on/off | Sets the default state (on/off) of the Num Lock key after booting. |
| USB permissions | Modifies USB speed and how many ports are enabled. |
| Integrated peripherals (enabling/disabling devices and ports) | Enables/disables and configures motherboard-controlled devices: SATA ports, USB, audio, network. Also sets RAM reserved for onboard video. |
| Advanced BIOS options | Configures CPU/memory frequencies, front side bus, north/south bridge, chipset, and memory voltage levels. |
| SATA configuration | Views SATA values assigned by BIOS/UEFI, changes related options, and configures RAID. |
| Devices | Configures USB, SATA, video, onboard devices, and PCI; the M.2 slot might need to be enabled here for an SSD to be recognized. |
| Virtualization support / Virtualization technology / Secure virtual machine mode | Enables/disables virtualization so virtualization software can access extra hardware capabilities. |
| ACPI (Advanced Configuration and Power Interface) | Sets what happens on power loss, on an incoming modem call, or when a PCI/PCIe device or mouse/keyboard triggers a wake action. |
| Drive encryption | Sets the key used to encrypt hard drive data. The computer will not boot without the correct password, and the drive cannot be moved to another computer without it. |
| LoJack | Security feature: locate the device, lock it remotely, show an 'if lost' message, or delete data if the device is stolen. |
| Intrusion detection / notification or Chassis intrusion | Notifies you if the computer case has been opened/removed. |
| Secure Boot | Checks every driver before launching drivers and the operating system, to block an unauthorized OS or software from loading during boot. |
| iGPU | Configures how much memory is allocated to the integrated GPU. |
| Built-in diagnostics | Runs diagnostic tests on hardware components, the hard drive, memory, the battery, and more. |
| Trusted Platform Module (TPM) | Enables the TPM chip that generates/stores cryptographic keys and passwords; can be cleared with TPM Clear. You may also see fTPM (firmware TPM, using the CPU instead of a separate chip) or a PTT option. |
| Security options | Grouping of the various security-related settings above (varies by manufacturer). |
A user password only allows minor changes (like boot order or date/time); a supervisor/administrator password allows viewing and changing all Setup options.
Secure Boot - it can block operating systems/loaders that are not authorized/signed.
In the Devices setting of BIOS/UEFI Setup.
Exiting without saving the changes made.
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TPM comes in two main versions, 1.2 and 2.0. Version 2.0 is a worldwide standard, though each manufacturer's UEFI menu lists TPM options a little differently. Enabling TPM through UEFI means selecting/enabling it, either as a physical module or through firmware. You can also clear the TPM.
Clearing the TPM turns it off and invalidates ALL existing security keys - this can cause loss of access to encrypted data. Always back up your data before clearing TPM. If you only want to turn TPM off without losing your keys and data, disable it instead of clearing it.
During boot, each component is checked for boot drivers, rootkits, and malware, and the TPM stores this information. UEFI's Secure Boot option, BitLocker Drive Encryption, and Windows Defender all make use of the TPM. Once TPM is enabled, you can start the TPM initialization wizard by typing tpm.msc in the Windows search box; you will be asked to create a TPM owner password, which can be saved to removable media and/or printed. This information is very important and cannot be recovered if lost.
Settings changed in system BIOS/UEFI are recorded and stored in a complementary metal-oxide semiconductor (CMOS) chip, found in the motherboard chipset. CMOS is memory that needs a small amount of power - supplied by a coin-sized lithium battery (the CMOS battery) - when the system is powered off. CMOS holds the settings configured through BIOS/UEFI. When the battery dies, all configuration information in CMOS is lost and must be re-entered (or the system relearns it) after the battery is replaced.