by Jimmy Greystone - 5/7/12 4:49 AM
The problem is more likely that only the very last PPC models to come out supported booting via USB at all, and then it was only if you went quite a ways out of your way.
I'm highly skeptical that it has anything to do with the journaling. The filesystem itself is the same, all journaling is, is basically the filesystem writes down what it plans to do, then does it. It's a purely optional function, and in fact you can turn it on/off in OS X on a whim with Disk Utility. So if for some reason you were trying to use a journaled filesystem on an older version of Mac OS X that didn't support that, it should still be able to access the drive. You just wouldn't have the added fault tolerance of the journaling. All the journaling really is, after all, is a special log file on the drive where the commands the filesystem is going to carry out are written down. That way if the process is interrupted, it knows what it still needs to do. When you look at what it actually is, it's really far less impressive than most make it out to be in their minds.
So the more likely scenario here seems to be that yours is not a model that can do booting off of USB.