USB-C Monitor on a Desktop with Discrete GPU

Question

There are lots of monitors now that offer a "all-in-one" cable solution via USB-C that carries power, display and hub capabilities over that single cable. This is fairly straightforward for a laptop that is advertised as Thunderbolt 3 compatible, but not so much for a desktop setup. Assuming the desktop has a discrete GPU, which of the following scenarios is correct:

1. This solution does not work on desktops: separate cables need to carry the separate feeds (power, display, data)
2. The GPU needs to have a USB-C port and can deliver power and data on top of display
3. The mainboard can channel the display feed from the GPU into its own USB-C port

Solution

The biggest difference between notebooks and “full-grown” PCs is the power draw. USB-C displays are typically designed to provide power over USB-C, to charge the notebook, essentially making the display a “docking station”.

USB-C Power Delivery, with up to 100 W, could be used to power the display. But that’s something the display has to support. I’m not aware of displays that do.

As such:

1. Yes, you need at least two cables to your display: display+data (USB-C DisplayPort Alt Mode) and power.
2. Yes, though power isn’t going to happen. An alternative would be a USB-C add-in card that is connected to your GPU via DisplayPort (outside the case). (sorry for the German source)
3. Yes, but only with the CPU-integrated GPU. This isn’t going to work with a dedicated graphics card except as outlined in 2.

Thunderbolt is typically not involved at all with this field. DisplayPort Alt Mode is enough: It carries DisplayPort + USB + Power.

Update: Found a “powered by USB-C” display after all: ASUS MB16AC. It’s not a desktop display though.

Comments

[ystan-]

can you elaborate on #2 in terms of on the purpose of the add-in card and what the connections would look like? is it GPU -> (USB-C/DisplayPort/?) cable outside case -> Add-in Card -> USB-C cable to monitor?

[ystan-]

understood on #1 that the power draw is the other way. on #2 and #3, lots of modern GPUs have usb-c ports so i'm not quite sure what you mean by the "GPU in the cable" as that kind of makes no sense to me. assuming #3 does not work, wouldn't it just be the mainboard's integrated GPU listed if you use the mainboard's USB-C port?

[Daniel B]

It’s graphics card -(DisplayPort)-> USB-C AIC -(USB-C)-> wherever. It’s for graphics cards that don’t have USB-C. There are also motherboards with DisplayPort-In for this purpose.

[harrymc]

I never saw a video card with a USB-C port, you might be referring to USB-C ports on monitors, which are something else where the monitor just doubles as a hub and requires a USB-C connection to the computer, just a built-in hub. For the mainboard USB-C port, you would need a cable such as this random cable which will appear to Windows as a second display adapter, and it does have a simple one inside that box.

[Daniel B]

There are now plenty of graphics cards (NVIDIA RTX 2000 series) with USB-C output. USB-C can carry DisplayPort. There is no DisplayLink or anything involved.

[harrymc]

@DanielB: Thanks for the info, although I don't think I'll see an RTX anytime soon.