Not too much, just one thing: If we could simulate the universe then of course there would be a simulation in the simulation, etc... And maybe there is a fundamental yet undiscovered 'law of computation' that a sufficiently complex simulation can embed itself only on a slower timescale, so even if everything is deterministic, we even theoretically cannot calculate fast enough to calculate the future.
Embedding itself is one thing, but what about embedding a small portion of itself? Suppose the area to be simulated was merely the Solar System (with the rest faked), and the size of the computer far larger...
