BIOSUEFI

BIOSUEFI refers to the firmware interfaces that initialize hardware and start the operating system on modern computers. The term encompasses both the traditional BIOS (Basic Input/Output System) and the newer Unified Extensible Firmware Interface (UEFI), which has largely displaced BIOS in contemporary systems.

BIOS is the legacy firmware that performs the Power-On Self Test, initializes CPU, memory, and devices, and then loads a boot loader from the disk’s Master Boot Record. It operates in 16-bit real mode and is constrained by limited addressable memory, making it less flexible for modern hardware and features. BIOS settings are traditionally stored in a CMOS battery-backed memory.

UEFI is a standardized, modular firmware interface designed to replace BIOS. Developed under the UEFI Forum, it provides Boot Services and Runtime Services, supports 32- or 64-bit execution, and uses the GUID Partition Table (GPT) and the EFI System Partition to store bootloaders (with .efi extensions) and drivers. UEFI enables faster boot times, larger and more flexible hardware initialization, graphical or text-based user interfaces, network boot, and advanced features such as Secure Boot, which authenticates bootloaders and drivers.

Key differences include UEFI’s driver model, virtual memory support, and GPT-based disk layouts versus BIOS’s legacy MBR. Compatibility is maintained through the Compatibility Support Module (CSM) to emulate BIOS on UEFI systems for older OSes. Open-source implementations (for example, TianoCore/EDK II and coreboot) coexist with vendor-specific firmware.

In practice, most modern systems use UEFI with Secure Boot and GPT, while BIOS remains referenced in legacy contexts or on very old hardware. The firmware continues to expose configuration interfaces and can influence boot behavior and system security.