I plugged my second monitor yesterday and I started having weird issues. The fps drop every now and then while playing games (or at least where I notice it). It happens every 10-15sec, the fps will drop in the ~30 fps range for around 5 sec. It is noticable and somewhat irritating.
The second monitor has a VGA cable with a DVI adapter plugged in the GPU. It's 1680x1050 as opposed to my main monitor at 1920x1080. I'm not an expert in that kind of stuff and I'd rather just unplug it than deal with it.
The ASUS monitor is plugged with an HDMI plug in the graphic card, there's only 1 HDMI port on the GPU.
The Venturer monitor is plugged in the DVI-I port on the graphic card. There's also a DVI-D plug but the small paper coming with the card told me to not plug VGA/DVI adapter in the DVI-D (and the metal thingy don't match anyway).
The weird pixels are only on the ASUS but they don't affect the performance. Here's a small example of what it does when I'm scrolling slowly (keep in mind I had to edit in photoshop since it can't be printscreened). http://i.imgur.com/XIZkv7q.png
Both monitors do show up in the control panel. After discussing with a friend, I was told the Venturer is a TV screen and might be why it's harder for the GPU to deal with it.
The fps problems happens on both monitors, it's directly related to game performances. All the fps monitoring apps show a clear 60 to 30 fps drop.