Would you agree that one possible route to uFAI is human inspired?
Human inspired systems might have the same or similar high fallibility rate (from emulating neurons, or just random experimentation at some level) as humans and giving it access to its own machine code and low-level memory would not be a good idea. Most changes are likely to be bad.
So if an AI did manage to port its code, it would have to find some way of preventing/discouraging the copied AI in the x86 based arch from playing with the ultimate mind expanding/destroying drug that is machine code modification. This is what I meant about stability.
Er, I can't really give a better rebuttal than this: http://www.singinst.org/upload/LOGI//levels/code.html
ITT we talk about whatever.