First, pc specs:
CPU: i7-3820 @3.6
GPU: 2x SLI GTX 670 Evga
64bit win 7 pro
32gb ram
I use a setup with 2 monitors + Cintiq (so technically 3 monitors, although Cintiq is turned off when not in use), both 1920x1080.
I am able to run pretty much every game on the max settings (only use one monitor for games, second is for watching stuff/chatting while i play). However if the second monitor has something on fullscreen (i.e. youtube, twitch stream, etc), then the fps in my main monitor game drops down significantly. If the second monitor's video is in windowed mode, stretched to fullscreen, everything is fine - only "full screen" full screen is affecting the fps.
Im wondering, is this normal? What could be causing this?