I have a feeling this is something game developers have taken care of themselves. Probably setting the cores to not sleep when they launch the game.
But with FX it was important in the early days of bulldozer (I think, might have the code names mixed up) Something to do with the way they changed the scheduler from piledriver, so that Windows wouldn't call it correctly. (To do with the core arrangement on FX chips, made it much worse for AMD) It was fixed in updates to Windows, but I recall a lot of gamers still recommending it at the time, even on Intel chips.