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Controlling boot behavior on a Mac

by David Hostetler [posted 20100419:11:33 (Mon)]

The annoyances of Apple-topia continue to pile up.  This time, I wanted to get a G5 to boot off of a CD.  How hard can that be?  Well, considering that there's no BIOS prompt or really any on-screen indicators of any kind, pretty damn hard.

So I had to go google up whatever arcane key combinations existed that would let me exert some influence on the machine's boot behavior.

Note: the following options are available on any Mac with 'New World' Open Firmware.

 

Action Key
Eject the CD tray Hold down the mouse button while booting.
Select boot device
  1. Hold down the ALT key (OPTION on mac keyboards) while booting.
  2. You should subsequently see an icon menu of bootable devices.
  3. Use the mouse to select the desired device, and then click the arrow to continue.
Get OpenFirmware prompt Hold the Command-Option-O-F keys while booting.
Reset PRAM and NVRAM to default values
  1. Hold the Command-Option-P-R keys while booting. You must press this key combination before the gray screen appears.
  2. Hold those keys down until the computer restarts and you hear the startup sound for the second time.
  3. Release the keys.

Apparently it may take 3 or 4 attempts at this to fully reset the memory.