12in G4 PowerBooks can't boot from external USB drives

Last year I partitioned the drive of my aging G4 PowerBook (12in Aluminum) and set it up as a dual-boot Ubuntu/OSX system. I've been pretty happy with this arrangement, but I haven't been using OS X much, really only to do some music with Ableton Live (no Linux version). So I decided to move OS X off onto an external drive and use the entire internal drive for Linux. My plan was to get a nice new Maxtor OneTouch 4 mini 500GB to act as the new backup drive for my Linux systems, and use the old Maxtor OneTouch 4 mini 120GB as the new external OS X drive.

After backing up both of the partitions, I was unable to boot into OS X from the external drive. I tried a bunch of things, starting with holding down the Option key to get that boot disk menu. I googled around and found a helpful discussion on the Ubuntu community site about someone else who is trying the same thing. This advice didn't work either. I got the following error:

$ ofpath /dev/sda1
/pci@f000000/ata-6@d/disk@0:4,\\ofpath: No such file or directory.

After googling around some more I found another posting about booting PowerPC Macs from external USB2 drives, this one from the OS X perspective. It was very helpful, but after reading it and booting my powerbook into openfirmware, it looks like it wasn't going to work.

Reading down the page and some more googling confirmed that the 12in Aluminum G4 PowerBooks can't boot off external USB drives.

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