A human brain simulation with a cognitive tick rate a few orders of magnitude faster than that of the human brain, with access to the internet, would appear to suddenly know everything that humanity knows at the moment of its inception.
This is because they could research, study, learn, carefully articulate and then plan out a verbalized response for any question that you asked them, in less than the time it takes a human to respond normally in real time.
They could then get back to solving all the world's problems while they awaited your long drawn out vocalization of a response over the course of what to them seems like hours.
A human observer could ask a question to the simulation that is unknown to the simulated mind. The human observer, seeing the real time accurate response to a complex question would likely be unable to distinguish between an all knowing AI and a super fast AI.