Game lag when using second monitor

[kananwest06]

When I play a game such as Euro Truck Simulator 2 on my primary monitor, it runs just fine. However, when I try to play the game on my secondary monitor, the game runs with a really slow frame rate and high lag.


Any help will be much appreciated.

 

[popatim]

What is your primary display connected to?
What is your secondary display connected to?