QUOTE(Madhatta @ Dec 23 2010, 02:17 AM)

Is it ok to do this before performing the NAND read and write? I am at the point that I have the JTAG wiring installed and am waiting for my flasher to arrive.
Would like to do this while I am waiting for the USB flasher to arrive but want to make sure this is OK to do prior to writing freeboot to the NAND. That way I can reassure myself that the box still boots and all that before the flasher gets here and I move on to that soldering.
you can; this will only prevent a normal update (hence blowing efuses). if you do accidentally update the normal way; the update will fail and leave you with a not working xbox. you will get stuck in an loop in which the xbox tries to update but can't; hence not booting to the dashboard.
then you have to go back to the usb/lpt wiring; and reflash your xellous/freeboot image again. and it then works just fine.
this is meant as a failsafe to prevent accidentally blowing efuses making your jtag exploitable xbox unexploitable