On desktop machines which has a monitor connected to both Nvidia/AMD discrete graphics and Intel on board Graphics card, it is recommended to always connect the Primary monitor directly to the Discrete GPU.
To review which GPU is currently connected to the primary monitor (Win 8.1 or Win 10), right-click desktop and select “Screen Resolution”. View which monitor is the primary by looking at which screen has the added icon group. You will also find a text telling if the selected display is your main monitor. Check to see if that monitor is connected to the Nvidia/AMD GPU, if not then you can change this in two ways:
1. If you wish to keep the position of the actual monitor assigned as the primary monitor, then go ahead and simply change the wiring so that the DVI or HDMI input on that screen is connected to the Nvidia GPU.
2. Alternatively, you can click on the secondary monitor, make that primary by checking the checkbox to make it your main display and ‘apply’ settings. But doing it in this way will switch your main view monitor.