After spending some time with Dell support and getting bumped up a few tiers, I got an customer service rep to explain to me that when a laptop has USB-C and HDMI output usually one of those ports is hard wired to the NVidia GPU and the other passes through the Intel GPU. Vendors have to decide to hard ware HDMI or USB-C. But in even on pass through scenario the Nvidia GTX is still handling all the rendering for both ports. If that last statement is true I don't understand why the Intel GPU pass through for TB3/USB-C is a show stopper for Rift S. Dell confirmed the USB-C/TB3 port should have even more bandwidth than my HDMI 2 port and with DisplayPort adapter TB3 should convert to DisplayPort 1.2 just fine. I'd like to understand the technical limitations and if we will ever see support for TB3\USB-C by way of DisplayPort adapter on laptops with a pass through on-board GPU configuration.
I'm not sure why it's a problem but it's a well known one and has nothing to do with Dell or the Rift. This is why most of us recommend a desktop if possible. That said, I'm using a laptop these days, no clue what my USB-C port is connected to but it also has 2x DP's to use as well, hopefully at least one of the three is connected to the GPU.
The basic idea is that the two GPUs (dedicated and integrated) are separate and have separate video memory. If the output (e.g. HDMI port) is wired to the Intel card, then if you do the rendering on the Nvidia card, the frame buffer will need to be copied over from one set of video memory to the other every single frame, which is a costly operation. In fact, it can be so slow that it might even be faster just to render on Intel, as crappy as that experience would be. From what I understand, it's a physical limitation of modern laptop design, I don't believe it would be possible to fix it in a software patch.
