It's really not obvious that if you run an AIXI-like AI it will actually do anything other than self-destruct, no matter how much juice you give it. There have been various papers on this theme recently and it's a common LW meme ("AIXI drops an anvil on its head").

I don't think it's obvious it would self-destruct - any more than it's obvious humans will not self-destruct. (And that anvil phrase is common to Eliezer.) The papers you allude to apply just as well to humans.

I don't think Tipler's not having heard of AIXI is particularly damning, even if true.

I believe you are the one who is claiming AIXI will never work, and suggesting Tipler might think like you.