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Open Firmware is a hardware-independent firmware standard based on the Forth programming language, used to boot a computer system. It initializes the hardware, performs diagnostics, and loads the operating system, while also building a "device tree" that describes the system's hardware configuration. Originally developed by Sun Microsystems for SPARC systems (where it was called OpenBoot), it was also popularized by PowerPC-based Macintoshes and is now often found in high-security workstations and servers.

Key functions and features

Hardware-independent standard: Open Firmware provides a consistent way for systems to start up, regardless of the specific hardware architecture.

FCode: It uses a bytecode format called FCode, which is independent of the instruction set architecture. This allows a single PCI card to include boot-time diagnostics and drivers that can run on different Open Firmware systems.

Device tree: It creates a detailed hardware description called a device tree, which helps the operating system understand the computer's configuration without needing to rely on hardware polling.

Forth-based interface: Open Firmware includes an interactive command-line interface based on the Forth programming language, which allows for advanced debugging and system maintenance.

Vendor adoption: It was adopted by various companies and systems, including Sun Microsystems (SPARC), Apple (PowerPC Macs), and IBM.