According to the official tech specs, the Dell Latitude E6420 uses the Intel® HD Graphics 3000 and the Dell Latitude E6430s uses Intel® HD Graphics 3000 for Intel Core i3 Processors and the Intel® HD Graphics 4000 for Intel Core i3/i5/i7 3xxxM Processors.
So I assume that if the behavior is not the same as the Dell Latitude E6420, you are using a Dell Latitude E6430s with the Intel® HD Graphics 4000.
Looking at this support thread on Intel’s site it seems like you are not alone in the confusion and there is an answer from “rtm_tech” which states:
This information is straight from the Configuration 3-Displays FAQ
page. For the Intel HD 4000 to actually support the three independent
display configuration, the following criteria need to be met:
- If two of the displays are DisplayPort* monitors
- If one of the displays is an Intel® Wireless Display (Intel® WiDi)
- If the built-in display is an Embedded DisplayPort1 (eDP) not a LVDS
That answer refers to the “Configuration 3-Displays FAQ” which describes itself as:
This document lists many of the possible ways to connect a computer to
three displays and the ways to optimize your viewing experience.
So I would recommend looking through that to see what you might have to adjust to get your Dell Latitude E6430s laptop setup just the way you would like it to.
Additionally this thread on the Dell support site refers to driver issues and the answer from “NIH tech” states:
I just discovered the answer today: I had previously checked video
card updates, and found two, and installed them. But in re-checking I
found that they were for 32 bit Windows OS - the laptop I was having
problems with has the 64 bit OS. Once I downloaded and installed that
driver fix - problem solved!
But again, that is just a clue as to what might be happening. Perhaps it’s a simply configuration misunderstanding on your part? Perhaps it’s a driver issue? Hopefully this info will set you on the right track.