Free BIOS implementations

coreboot (formerly LinuxBIOS) is an open‑source project that provides lightweight firmware to initialize hardware and then load an operating system. It is designed to replace proprietary firmware (traditional BIOS or UEFI implementations) by performing the minimal tasks required to start a modern 32-bit or 64-bit operating system.

Libreboot (briefly known as GNU Libreboot) is a free and open-source software project based on coreboot, aimed at replacing some of the proprietary BIOS or UEFI firmware on supported x86-64 and AArch64 computers. Libreboot performs the basic machine setup such as CPU initialization or memory controller initialization necessary to load and run a 32-bit or 64-bit operating system, such as Linux or BSD. It was tested on FreeBSD, NetBSD, and OpenBSD.

OpenBIOS is a project aiming to provide free and open source implementations of Open Firmware. It is also the name of such an implementation.

LinuxBoot is a free software project aimed at replacing most of the Driver Execution Environment (DXE) modules in Unified Extensible Firmware Interface (UEFI) firmware with the Linux kernel. LinuxBoot must run on top of hardware initialisation software in order to start. This can be the Pre-EFI Initialization (PEI) part of UEFI, coreboot, or U-Boot. It can boot Linux through the kexec syscall, but is also able to boot Windows with a different method.

SeaBIOS is an open-source implementation of an x86 BIOS, serving as a freely available firmware for x86 systems. Aiming for compatibility, it supports standard BIOS features and calling interfaces that are implemented by a typical proprietary x86 BIOS. SeaBIOS can either run on bare hardware as a coreboot payload, or can be used directly in emulators such as QEMU and Bochs.