On Premieres and later models it's the CPU, not a separate encryption chip like earlier models. On Series 2 & 3 models it "only" required a surface-mount rework station. Switching the main CPU on later models is possible if you can swap BGA (ball grid array) chips without destroying them, but how many people have the skills and hardware to do that reliably?Unfortunately the original question was not answered. There must be some yet-to-be-identified surface mount chip(s) that can be swapped using a solder rework station in order to bring another board up with the same serial number personality. I had an Premiere that had a motherboard failure and another unused unsubscribed Tivo with identical board part numbers and revisions. Made me wonder which chip(s) I needed to swap out to make it take on the same s/n.
>(specifically I think it's tied to information burned into one of the non-removable chips on the motherboard)
Every chip is removable with the correct equipment.