> I think "entropy" is used to mean "unpredictable in principle", which would exclude chaotic processes like CPU jitter. Chaotic processes like the weather are

> I think "entropy" is used to mean "unpredictable in principle", which would exclude chaotic processes like CPU jitter. Chaotic processes like the weather are predictable in principle; but they are so complex that in practice they are unpredictable. Chaotic systems are practically unpredictable because they have an exponential dependence on their initial conditions. It has nothing to do with complexity -- a double pendulum is a very simple system and is still chaotic. In other words, as you evolve t, you need more and more bits of precision in the state variables of the initial condition in order to continue predicting the future state correctly. As soon as you start drifting away from the real state the gap between your prediction and reality exponentially increases. As there is a physical limit to what accuracy you can measure things, at some point is becomes physically impossible to continue accurately predicting the future state.