I recently hooked up a second monitor, and it's been invaluable for productivity tasks like doing homework and looking up stuff about a game while playing it. The problem with games is that ever since I put the second monitor on, the games have been running significantly worse.
I have a GTX680 2GB. Both monitors are connected to the gpu via DVI cables. All games are being run from the primary monitor.
Sometimes games will run at half speed and then back up with no noticeable dip in gpu usage. Oddly enough, games will perform MUCH worse in fullscreen mode, but will run almost fine in windowed. Even if I stretch the game across both monitors, it runs better than being fullscreened to one. For example, Need for Speed: Rivals never dipped below 30 in all the time that I played it when it came out, but with two monitors it dips below all the time, sometimes dipping below the 20s while using less than half of the gpu. When I alt+tab out of the game, it runs perfectly fine in the background.
And then to top it all off, when games (or videos) are being run on the primary, the secondary monitor suffers from extreme lag and framerate issues. I can't play a game and watch Brad die in Demon's Souls without extreme stuttering on the latter.
I'm not sure at all on what to do about this. Some people on the Internet say that there shouldn't be any problems with a second monitor while others say there are. Is there a solution to this, or have I joined some horrible club that I have to get used to?