G4 Cube Boot ROM

Anything not about Mac emulation.

Moderators: Cat_7, Ronald P. Regensburg

Post Reply
Space Cadet
Posts: 1
Joined: Sat May 02, 2020 2:49 am

G4 Cube Boot ROM

Post by nebular »

A mosfet blew on my Cube and in the process of diagnosing and repairing, I discovered that the Cube has a DAC on the motherboard. Further investigation shows that it also has an audio amplifier connected to the analog outputs on that DAC and the amp is connected to the 2-pin connector in front of the RAM (which is where the speaker was connected on the Cube prototype). The DAC digital lines are still connected to the rest of the board as well. Everything I'm seeing is saying that the DAC is disabled in firmware not hardware. The only thing I've found on the DAC on the cube is that it was needed to get the startup chime to work then everything else was handled by the usb audio device once the OS started up.

So I'm trying to figure out how to get the DAC and speaker connection working. My suspicion is that the DAC is started up during the boot post phase then after the chime is played, but before Open Firmware is loaded it's shutdown again.

I'm no hardware hacker, I barely know how to program, but I'm taking on this challenge and am willing to learn. And the first thing I need to know is how to dump the boot ROM from the motherboard, as OF doesn't see the DAC and after OF is loaded everything for a new world rom is pulled from a file on the hard drive.

So can anyone help me in dumping the Boot ROM from my Cube?
Post Reply