You will need 8gb to 16gb hdd or flash drive for the OS, it's your decision to pick where you want to boot from, also every other tools are available in the OS, overclocking, flash bios and others
I'd probably put it onto my spare 250 GB SSD, but I would really prefer to run it off of a USB and keep my drive somewhere else. Do you need a USB 3.0 drive so that it's fast enough? So you would use the OS to do the tuning instead of the AMD drivers? Does it automatically override them or something? Thanks for the replies.
Let me tell you. Drop USB and go get yourself a couple of cheap SSD drives, 60GB or 120GB, new or used. They are not that much money and will pay you back in time saved. They are way faster and more reliable than any USB.
Dont screw around with USB, its not worth it.