The alternate modes is where USB-C and Mini DisplayPort connectors can get a bit tricky.

Thunderbolt 1 and 2 use the Mini-DisplayPort connector in an alternate mode, with DisplayPort running over the wire for monitors. Thunderbolt busses typically let you attach a non Thunderbolt DisplayPort monitor at the end of the device chain. TB1/2 only really saw adoption on Macs, only a handful of PCs supported it.

Thunderbolt 3 swaps to using the USB-C connector. Both Thunderbolt 2 and Thunderbolt 3 cap out at the Displayport 1.2 spec. The DP version becomes important when talking about high resolution monitors. And at this point the only devices that support TB3 are a growing number of PCs. Macs will likely ship with it later this year.

Thunderbolt is what supports device chaining, where one connector on the computer can have up to 6 devices attached to it. Normal USB over USB-C connectors still uses a hub model and not chaining.

USB-C alternate mode also allows pure DisplayPort 1.3 with no Thunderbolt. DP 1.3 adds some 5k and 8k monitor support, along with higher refresh rates for 4k monitors. DisplayPort 1.2 (and above) offers both chaining and a hub model, independent of USB or Thunderbolt.

And then there's one more way to directly drive a display over USB-C, using the MHL alternate mode. This is likely to only show up in mobile phones/tablets as this is historically where MHL has been used before and tends to be adapted into HDMI.

For Thunderbolt or DisplayPort modes over Mini DisplayPort a USB-C connector, the GPU in the computer is what is ultimately driving the monitor. Monitor and resolution limits will be decided by the built in GPU. Or to throw more complexity in, possibly by an external GPU plugged into the Thunderbolt interface (like the Razer Core). Due to Thunderbolt carrying DisplayPort, the built in LCD of a laptop could be driven by an external GPU.


And as discussed elsewhere in the thread, you then have pure USB 2.0/3.0/3.1 over USB-C, and the ability to use DisplayLink GPUs as an external GPU. Monitors plugged into these are driven directly by the DisplayLink GPU and not the computer's GPU. It's a good way to get around the limits of a built in GPU. This can come at a cost of CPU time though. Also due to normal USB not carrying a video signal over it, DisplayLink devices cannot drive an internal LCD on a laptop, only monitors directly plugged into the DisplayLink device. Oh, and don't be surprised if you come across a monitor that has a DisplayLink chip directly inside it.


It's all clear as mud. Basically for your clients Matt, you will have to know exactly what type of protocols their USB-C ports support to be able to offer a good solution. Especially if you are factoring in possible 3d graphics/gaming desires on the display. It's pretty much a non starter if DisplayLink is involved.