firmwareBIOS

Firmware BIOS is the system firmware responsible for hardware initialization and bootstrapping a computer. It resides in non-volatile memory on the motherboard and runs before the operating system, performing power-on self-test, hardware enumeration, and the initial loading of the bootloader.

Historically, BIOS referred to a 16-bit firmware interface used by IBM PC compatible systems. Newer systems often use UEFI (Unified Extensible Firmware Interface), which provides a more modular interface, faster boot times, and support for larger boot partitions. Many systems still offer a compatibility support module to run legacy BIOS code within a UEFI environment.

Operation and features: On power-up, the firmware performs POST, initializes the chipset, memory, and devices, and then transfers control to the operating system’s bootloader via the appropriate boot mechanism (such as MBR or GPT). It may also provide runtime services to the operating system and expose a firmware setup utility for configuration, whether labeled as BIOS or UEFI.

Update and reliability: Firmware updates are delivered as flashable images that replace the code in the ROM/flash chip. Updates can be applied through vendor-provided utilities in the operating system, through bootable update tools, or via the UEFI interface. Updates carry risk: a failed or interrupted update can render a system unbootable, so manufacturers stress power stability, proper procedures, and signed, authenticated images.

Security: Modern firmware implements features such as Secure Boot, measured boot, and cryptographic signing to protect the boot process. Firmware remains a critical attack surface, so integrity checks and secure update mechanisms are emphasized to mitigate firmware-targeted threats.