If you see horizontal or vertical green lines on your screen as show below, it means that you have selected the control advanced control panel mode. ( View-> Advanced. Select ),"Show SLI Visual Indicators" enabled in the NVIDIA Display control panel -> 3D Settings -> Set SLI configuration -> 3D Settings pull down menu. When enabled, this option shows how your GPUs are sharing the graphics load. For games that are rendered using AFR (alternate frame rendering), a green vertical bar will grow up and down on your screen, depending on the amount of scaling. For games that are rendered using SFR (split-frame rendering), a green horizontal line will move up and down on your screen, showing how the load is being balanced between each GPU. If the upper half and the lower half of the screen have a similar level of detail, the horizontal line will stay close to the middle.