Energy saver mode when playing games?

Why do Mac games go into energy saver or power saver when playing games? I installed Jiggler, and I still have this problem. I've also turned off the energy saver and screen savers, and still it goes into Energy saver mode, and I can't get out of it. I have to do a hard shut down.

Could it be my monitor just going into power save mode? I'm at a loss.

Any ideas would be great.

check that you have set the right Energy Saver settings, there are two tabs, one for Battery and one for Power Adapter

I'm on a Macpro, so no battery, thanks though.