How to Access Open Firmware on a Mac

How to Access Open Firmware on a Mac

Standard for computer bootstrap code

Open Firmware
is a standard defining the interfaces of a computer
firmware
organisation, formerly endorsed by the
Institute of Electric and Electronics Engineers
(IEEE). It originated at
Sun Microsystems, where it was known as
OpenBoot, and has been used by vendors including Sun,
Apple,
IBM
and
ARM.
[1]

Open Firmware allows the system to load
platform-contained
drivers
directly from a PCI device, improving compatibility.

Open up Firmware may be accessed through its
command line interface, which uses the
Along programming language.

Open up Firmware is described past
IEEE
standard
IEEE 1275-1994, which was not reaffirmed by the Open Firmware Working Group (OFWG) since 1998 and has therefore been officially withdrawn by IEEE.

Several commercial implementations of Open Firmware have been released to the Open up Source community in 2006, including Sun OpenBoot, Firmworks OpenFirmware and Codegen SmartFirmware. The source lawmaking is bachelor from the
OpenBIOS
project. Sun’s implementation is bachelor under a
BSD license.
[two]

Features

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Open up Firmware defines a standard way to describe the hardware configuration of a arrangement, chosen the

device tree
.
[3]

This helps the operating arrangement to ameliorate understand the configuration of the host computer, relying less on user configuration and hardware polling. For example, Open Firmware is essential for reliably identifying slave
I2C
devices like temperature sensors for
hardware monitoring,
[4]

:§five.1
whereas the culling solution of performing a bullheaded probe of the
ItwoC
bus, as has to be done by software like
lm_sensors
on generic hardware, is known to result in serious hardware bug under certain circumstances.
[4]

:§v.ii

Open Firmware Forth Code may be compiled into FCode, a
bytecode
which is independent of
instruction set architecture. A
PCI card
may include a plan, compiled to FCode, which runs on any Open up Firmware system. In this manner, it can provide boot-time
diagnostics, configuration lawmaking, and
device drivers. FCode is also very meaty, so that a disk driver may require only 1 or two kilobytes. Therefore, many of the aforementioned I/O cards can exist used on Dominicus systems and Macintoshes that used Open Firmware. FCode implements
ANS Along
and a subset of the Open Firmware library.

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Being based upon an interactive programming language, Open Firmware tin can be used to efficiently test and bring up new hardware. It allows drivers to be written and tested interactively. Operational video and mouse drivers are the only prerequisite for a graphical interface suitable for end-user diagnostics. Apple shipped such a diagnostic “operating system” in many Power Macintoshes. Sunday as well shipped an FCode-based diagnostic tool suite chosen OpenBoot Diagnostics (OBDiag) used past client service support and hardware manufacturing teams
[5]

Access

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On Sun
SPARC
systems, the Open Firmware interface is displayed on the console concluding before the
bootstrapping
of the organisation software. If a keyboard is connected, the main video display volition be used as the console terminal and Open Firmware can be re-entered at any time by pressing
End+A
(L1+A) on the keyboard. If no keyboard is connected, then the first series line on the system is usually used as the panel and Open Firmware is re-entered by sending a “Break” on the serial line. While the arrangement software is running, various Open Firmware settings can exist read or written using the
eeprom
command.

On a PowerPC-based Macintosh, the Open Firmware interface tin exist accessed by pressing the keys
⌘ Cmd+⌥ Option+O+F
at startup (⊞ Win+Alt+O+F
if using standard PC USB keyboard).
Intel-based Macintoshes
exercise not apply Open Firmware; they use
Extensible Firmware Interface. Besides, early versions (before the
PowerBook 3400) connect Open Firmware’south input and output to the Modem port by default.[

citation needed

]

This functionality is generally only used past developers or troubleshooting I.T. personnel; for common users, the
Mac Bone X
operating system provides a high level
graphical user interface
to change commonly used Open Firmware settings. For instance, it is possible to specify the
kick disk
or
partition
without directly using the Open Firmware interface, but with some limitations (due east.g. it is not possible to select boot from USB mass-storage devices, but Open Firmware allows iMac to kicking using
kick ud:,\\:tbxi

command). Other Open Firmware settings tin be changed using the

nvram

control while the system software is running.
[vi]

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On
Pegasos, the interface is accessed by pressing
Esc
at startup.

On
IBM Ability Systems, Open Firmware (“ok” prompt) can exist accessed through the SMS Boot Menu. SMS Boot Menu can be accessed by pressing
1
or
F1
during the kicking sequence, after hardware checking, and merely before the Os boot.

On the
OLPC XO-1
laptop, Open up Firmware access requires a programmer key, that can be obtained subsequently registration with OLPC. Later on installing the key, upon each power-on, the boot inaugural can exist interrupted with
Esc
(the upper left key) to become to the Forth prompt.

See also

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References

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  1. ^



    Edifice Open Firmware for ARM


  2. ^




    “OpenBIOS”
    . Retrieved
    10 May
    2012
    .




  3. ^



    Mauro, Jim (2001).

    Solaris Internals: Core Kernel Components
    . Prentice-Hall Professional. p. 107.
    ISBN
    9780130224965
    .


  4. ^



    a






    b





    Constantine A. Murenin (21 May 2010). “5.1. Open Firmware and IiiC”.

    OpenBSD Hardware Sensors – Ecology Monitoring and Fan Control

    (MMath
    thesis).
    University of Waterloo: UWSpace.
    hdl:10012/5234. Document ID: ab71498b6b1a60ff817b29d56997a418.




  5. ^



    https://docs.oracle.com/cd/E19088-01/250.srvr/805-3389-11/6j37qsqsj/index.html


  6. ^



    Apple’south Transition from Open Firmware to Extensible Firmware Interface, mactech, 2007.

External links

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How to Access Open Firmware on a Mac

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