1) Don't do it yourself, for the love of god no. You'd solder the wrong stuff and end up with a heavy door stop.
2) JTAG's are only for offline modding.... Unless you want to buy XBLS (XBOX LIVE STEALTH) which is like $50 a day! So you'd better start paying =3.
3) XBOX One comes out soon... What's the point? lol
Just my input though... If you do want to go ahead with it... Buy a RGH XBOX or pay someone with knowledge to do it for you. RGH just means Reset Glitch, it's identical to a JTAG but works on all dash's
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