The ROM-in-RAM software architecture implemented on the Power Mac G4 computer follows some of the standards defined by the Open Firmware IEEE 1274-1994 specification. Three Technotes provide an introduction to Open Firmware on the Macintosh platform. They are:
TN 1061: Open Firmware, Part I, available on the Technote web site at
http://developer.apple.com/technotes/tn/tn1061.html
TN 1062: Open Firmware, Part II, available on the Technote web site at
http://developer.apple.com/technotes/tn/tn1062.html
TN 1044: Open Firmware, Part III, available on the Technote web site at
http://developer.apple.com/technotes/tn/tn1044.html