I am using a Lenovo laptop with Intel HD Graphics 4600 and attach it to a Lenovo docking station. I can run 2 monitors (1 VGA and 1 DVI) whilst the laptop lid is closed and the laptop is on the dock (cables attached to the back of the docking station). I recently purchased a mini-DisplayPort-to-VGA adapter which I have successfully used to drive a 3rd monitor whilst the laptop is closed and docked as long as I plug the miniDP into the side of the laptop. As the docking station only has DisplayPort and not mini-DisplayPort I then purchased a DisplayPort-to-mini-DisplayPort adapter and hoped to run all 3 monitors from the back of the docking station. This, however, does not work. From this configuration the best I have achieved is 2 of the 3 monitors being detected.
Can anyone comment on why I cannot drive all three from the docking station?
The 4th generation processors supports up to 3 monitors, meaning that in this case you will have the laptop monitor and two more to add.
Additional you can check the number of Displays Supported according to your processor on ARK | Your Source for Intel® Product Information.