@Markerrag -- good point, but that can be a hard question to answer. One of the misconceptions about multi-core CPUs is that they are designed to make computers faster by combining all of those cores into one, fast unit that will take on a task. That's not the point at all -- multi-core CPUs are faster because they can handle many different tasks at the same time.
Having said that, most operating systems are built on the old "system prioritization" model in which some tasks will always take precedence over others. If all cores are dealing with system tasks because of prioritization, then you don't have a truly real time operating system. In other words, the answer seems to be yes and no -- things can usually be done in real time, but tasks are still prioritized and that could cause some things to be delayed.