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Open Firmware: Difference between revisions
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Open Firmware is the process that controls the microprocessor after hardware initialization and diagnostics are performed, but before the main Operating System is passed control. It is responsible, among other things, for building the device tree and probing the expansion slots for I/O devices. Open Firmware queries [[PCI]] devices for its address space needs and dynamically assigns this space to each device. It is during this probing process that each device and motherboard ASIC is given a node in the device tree. | Open Firmware is the process that controls the microprocessor after hardware initialization and diagnostics are performed, but before the main Operating System is passed control. It is responsible, among other things, for building the device tree and probing the expansion slots for I/O devices. Open Firmware queries [[PCI]] devices for its address space needs and dynamically assigns this space to each device. It is during this probing process that each device and motherboard ASIC is given a node in the device tree. | ||
=Open Firmware Startup= | |||
The Open Firmware startup process in PCI-compatible Macintosh computers conforms to the IEEE Standard 1275 for boot firmware and the PCI Bus Binding to IEEE 1275-1994 specification. The Open Firmware startup process is driven by startup firmware (also called boot firmware) stored in the Macintosh ROM and in PCI card expansion ROMs. While the startup firmware is running, the Macintosh computer starts up and configures its hardware (including peripheral devices) independently of any operating system. The computer then finds an operating system in ROM or on a mass storage device, loads it into RAM, and terminates the Open Firmware startup process by giving the operating system control of the PowerPC main processor. The operating system may be Mac OS or some other system, provided it uses the PowerPC instruction set. | |||
=Documentation= | =Documentation= | ||
Revision as of 12:20, 24 June 2020
Open Firmware is the process that controls the microprocessor after hardware initialization and diagnostics are performed, but before the main Operating System is passed control. It is responsible, among other things, for building the device tree and probing the expansion slots for I/O devices. Open Firmware queries PCI devices for its address space needs and dynamically assigns this space to each device. It is during this probing process that each device and motherboard ASIC is given a node in the device tree.
Open Firmware Startup[edit]
The Open Firmware startup process in PCI-compatible Macintosh computers conforms to the IEEE Standard 1275 for boot firmware and the PCI Bus Binding to IEEE 1275-1994 specification. The Open Firmware startup process is driven by startup firmware (also called boot firmware) stored in the Macintosh ROM and in PCI card expansion ROMs. While the startup firmware is running, the Macintosh computer starts up and configures its hardware (including peripheral devices) independently of any operating system. The computer then finds an operating system in ROM or on a mass storage device, loads it into RAM, and terminates the Open Firmware startup process by giving the operating system control of the PowerPC main processor. The operating system may be Mac OS or some other system, provided it uses the PowerPC instruction set.
Documentation[edit]
- Fundamentals of Open Firmware, Part I: The User Interface
- Fundamentals of Open Firmware, Part II: The Device Tree