You may need to subdivide the drive into smaller volumes depending on
what the capabilities are of the G4 firmware and the version of Mac OS
you are running. When formatting it's important to check the bootable
box. I'd look all the details up but you can do that yourself.
On 07/01/2015
First, your DA G4 doesn't support volumes bigger than 128 GB.
My shop had four G4 DAs, and all supported 128 GB (actual capacity is
131,072).
You may use HD Speedtools, but that is an extension, and is only available
after booting has been successfully completed.
You may use the Open
