"
... the last person I spoke to in the industry said that the systems are still totally separate and as someone said earlier they only share a power supply.
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Not even the last is necessarily true. Large aircraft have at least 3 completely separate power busses, and the IFES is probably only connected to one of them. All critical systems are capable of switching to another bus (either manually or automatically) should the one they normally run on fail (though cascade failures have happened in unusual circumstances).
Biting the hand that feeds IT
