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So with Windows 10's "Project to This PC" Miracast stuff, I can use my laptop as a third monitor for my desktop. However, this is laggy, not the highest quality, and requires an active connection. If I had a hard-wired connection between the two systems, the effect would be much better.

My desktop's 1050 Ti has a DisplayPort output, and my laptop has multiple Thunderbolt 3-enabled USB-C ports. Theoretically, I can use this to output video from my desktop to my laptop, then simply transpose the video over my display on the laptop, creating a low-latency connection.

I have no idea if something like this exists (or if anything remotely similar to this has popped up). Anyone have any ideas?

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    I'm not sure but I don't think your laptop's GPU would support a video input. Usually, GPUs only output stuff. You would have to somehow create the cable from your desktop directly to the laptop's monitor, which isn't impossible but requires hardware modification and you wouldn't be able to fit all that in your laptop's case, so you won't be able to close it up anymore. (That's depending on how your laptop is connected to the display internally and might be impossible alltogether. But driverboards for most laptop LCD's exist, so sacrificing the laptop, it should be possible but far form ideal)
    – confetti
    Aug 27, 2018 at 23:56
  • @confetti My laptop is a Dell XPS 9370, all of the USB-C ports carry data. Would it be possible to emulate a monitor at the laptop end while catching the display data to the laptop? Aug 27, 2018 at 23:59
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    Handling video as an input requires specific chipsets on the hardware side, which I don't think any laptop comes with.
    – confetti
    Aug 28, 2018 at 0:02
  • @confetti That's unfortunate. Thanks anyway! Aug 28, 2018 at 0:03
  • cnet.com/forums/discussions/… - I've found this. But you can expect a very bad quality from that, and I'm sure your PC doesn't have a VGA output. You could use a DP to analog adapter but things are getting really expensive here and the quality you can expect is similar to a ten year old TV.
    – confetti
    Aug 28, 2018 at 0:07

3 Answers 3

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Theoretically, I can use this to output video from my desktop to my laptop, then simply transpose the video over my display on the laptop, creating a low-latency connection.

Theoretically, this is possible, but it would require two pieces of dedicated hardware on your laptop: (1) The ability to receive DisplayPort signals, instead of having the graphics card send them, and (2) the ability to overlay received data onto your display.

I've never heard about such hardware on a laptop. Apple doesn't really provide details on the hardware, so even if your hardware could do that (unlikely), you can't write drivers for it.

So, that won't work.

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  • I mean, external GPUs are a thing. Surely I can utilize that tech to accomplish this Aug 28, 2018 at 14:48
  • @IsaacCorbrey: The external GPU is using the Thunderbolt PCIe connection. So yes, you can use Thunderbolt to DMA stuff into your framebuffer (which is actually a security vulnerability). No, you can't do this with DisplayPort signals, you'll need a PCIe device at the other end. Yes, you can make a device that reads DisplayPort signals, and uses PCIe to DMA the data in, but I am not aware of such a device.
    – dirkt
    Aug 28, 2018 at 16:55
  • There are apps like duet display for android and ipad that can do a reasonable job of using a tablet as a second display via usb. They don't use specialist hardware.
    – Att Righ
    Sep 15, 2021 at 22:01
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and my laptop has multiple Thunderbolt 3-enabled USB-C ports. Theoretically, I can use this to output video from my desktop to my laptop

No, you can't output DP into your laptop's USB. Mostly because the laptop USBs are USB hosts, and secondly the USB ports can't "input" DP signals even if they are multi-functional TB/DP/USB ports, and the DP is an output. But you can output virtual display card over USB, which can be displayed on special USB displays.

To turn your laptop into "USB display" you need the laptop to be a USB DEVICE, and a special device. I don't know if your XPS 9370 suppports DRP modes (formerly known as OTG), but even if it can, it must implement the AV-class of USB devices with image rendering capability. While image rendering on laptop screen should be a relative no-brainier, the implementation of AV-Class on standard OTG device controller is very questionable. See some more details here.

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If you principally need to use a USB-C, this will require a USB Graphics Controller driver (WDDM). Try the solution from Fresco Logic: LCI Proxy driver (Github). Or use the classic options from DisplayLink via USB.

If you need a result and wi-fi is quite satisfied - a complete solution to the issue is SPACEDESK app.

Spacedesk even listed all similar solutions (see SIMILAR PRODUCTS).

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