Latitude E7470 docking DP port version

@Rocky_1982  The first generation E-Port docks used DP 1.1a.  The second generation E-Port docks used DP 1.2.  The way to tell them apart is the rear USB ports, since the second generation docks also upgraded those to USB 3.0.  So the second generation dock will have blue USB ports back there, while the first generation docks will have black USB 2.0 ports there.  The USB ports on the left side are always black and always USB 2.0.

The E7470 itself only sends a single DP 1.2 interface to the dock, though, so if you connect more than one display, the total bandwidth requirements of the displays have to fall within what a single DP 1.2 interface can run.  Some other systems compatible with the E-Port docks can send two DP 1.2 interfaces to the dock, but not the E7470.