Open Firmware

From Applepedia

Open Firmware is the IEEE 1275 standard for boot firmware and interface with hardware. Currently Sun and Apple ship hardware that use this software. It's similar to the BIOS setup on x86 hardware, but provides less functionality as these systems lack legacy hardware and software that need special support from the firmware.

http://playground.sun.com/1275/

http://www.openfirmware.org/

How To Clear Open Firmware Values On Your Mac

To clear all Open Firmware values that may be causing issues, such as poor battery performance on portables perform the following steps.

Clear your PMU:

1. Turn the computer completely off.
2. Hold down Shift-Control-Option and press and release the power button.
3. Wait 5 seconds.
4. Turn the computer back on.

Followed by these steps should clear all the settings your Mac has back to defaults:

1. As the computer is powering on, hold Command-Option-P-R until you hear the chime three times. It will take awhile between each chime.
2. After the third chime, switch to Command-Option-O-F to get into Open Firmware.
3. Run set-defaults.
4. Run reset-nvram.
5. Run reset-all. The computer will reboot at this point.

Open Firmware Song

Sing the Open Firmware Song (to the tune of the Flinstones theme song) when you're hacking away! It rivals the Free Software Song in nerdyness.

Firmware, Open Firmware
It's the appropriate technology

Features,
F-code booting,
Hierarchical devinfo tree.

Hack forth,
Using EMACS on the keys.

Save in,
NVRAM if you please.

With your, Open Firmware,
You'll fix the bugs in no time
Bring the kernel up in no time

You'll have an F-code time!

Useful OF Commands

• eject cd - Opens the CD tray/ejects the CD
• setenv boot-args X - sets the default OS X startup flags (-v for text console, -s for a single user prompt, io=0xff to display way too much information)
• reset-all - Restarts
• setenv load-base 0x700000 - Probably prevents your computer from booting. May prevent it from ever booting again.