I don't remember any PowerPC Macs that wouldn't allow me to enter Open Firmware. (The early beige series machines, G3 and below, sent the output to serial port, not screen, by default. It was possible to change once you got there.) Some machines require accurate timing to get into Open Firmware. Try waiting about 5 seconds, after hearing the chime, before pressing down cmd-opt-o-f. What is the exact model you have? Risto