Ok, Here is another real world example. This time its playing Left 4 Dead 2 on maximum settings. The game suddenly throttles at the game plays slow. Note, then it becomes playable again. Note, that it is exactly the same environment with exactly the same number of NPC's. That means it should perform the same, but the throttle is to blame.
Also, note, L4D2 is one of the most popular games right now. Its not synthetic