A quick google search http://www.google.com/search?hl=en&q=open+firmware will give you more than enough info.
http://playground.sun.com/1275/ (IEEE 1275)
Macs have been using Open Firmware since they moved to PCI hardware (PowerMac 7500, etc)
© 2016, O’Reilly Media, Inc.
All trademarks and registered trademarks appearing on oreilly.com are the property of their respective owners.