@bmike according to MacTracker: if it's an Intel-based MacBook from the 10.4.x era, then it'll be Intel Extensible Firmware Interface (EFI). AFAIK we won't find both Open Firmware and EFI on a Mac.

… maybe I'm wrong; support.apple.com/kb/HT1471

@bmike I hope you don't mind, I rolled back your apple.stackexchange.com/revisions/93223/2 - Command-Option-O-F is for a prompt (not for a reset).

Anyone: please vote down my misleading and potentially destructive answer at apple.stackexchange.com/a/93384/8546

@GrahamPerrin Excellent - it was hazy and not entirely accurate.

How does it look now? apple.stackexchange.com/posts/93223/revisions