I’ve also noticed that. But from what I’ve seen, blender takes the maximum of the CPU he can, but don’t seem to use it. I think that it’s the “outside” line in the debug properties, which correspond to what is not really used. So in fact you can look at a video in the same time you’re playing without noticing any slowdown.
Indeed, the BGE takes all the CPU: when all the tasks are done for a frame, it just loops to consume the remaining time until the next frame. That does not prevent the CPU to do other things as superrom said.
is there a way to prevent blender from looping like that after all the tasks are done for a frame? it might help my laptop in the long run… someone on irc was suggesting a python script with a sleep() function? what do you think?