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nVidia dGPU can't be used over USB-C
Alienware 15 laptop. I'm using the current Thunderbolt 3 port with the proper full speed cable. For whatever reason, any monitor connected via USB-C can't be seen nor used by the nVidia dedicated GPU.
How may I solve this?
jphughan
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December 6th, 2018 17:00
Looks like the USB-C display output is physically wired to the Intel GPU rather than the NVIDIA GPU. Unless your system has a BIOS option that Dell calls “Graphics special mode”, this is a hardware property of the system that you can’t change, and to my knowledge that BIOS option is only available on recent Precision 7000 Series models. They have DisplayPort multiplexers on the motherboard that allows you to change which GPU controls various display outputs, but that is a very rare design.
That said, that doesn’t mean that your NVIDIA GPU can’t be used to accelerate content on the display attached via USB-C. Most laptops with dual GPUs these days have all outputs wired to the Intel GPU, but the NVIDIA GPU can still act as a render-only device that passes completed video frames to the Intel GPU for transmission to the display. It’s called NVIDIA Optimus and it has existed for quite a while now. There are still some applications that don’t work well with this, and there are also certain technologies supported by the NVIDIA GPU but not the Intel GPU that consequently don’t work with this “Intel passthrough” setup (VR and G-Sync to name two), but unless you need those technologies or are using a problematic application, you should be fine. And if you ARE in that situation, you might find that another display output is wired to the NVIDIA GPU. If you open NVIDIA Control Panel, there should be a section that shows which outputs are wired to which GPU.
bwritter
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December 6th, 2018 20:00
That's very informative, thank you. Of all the applications to work with Optimus I would expect Photoshop to be one of them. Luckily, Photoshop has a readout of which GPU it's taking advantage of so I can try some things in the morning. My knowledge as of now was I was getting severe performance drops using the basic tools on that monitor, even in 1080p. But that GTX 1060 really should be enough to drive PS at 4K reasonably. I'll run some tests and report what I find.
Nyxnight
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September 1st, 2019 08:00
Is there no hardware workaround for this issue cuz i bought a monitor recently for a lot of money and now i cant use any of the nvidia features and also will using an external gpu and dock solve this issue.
jphughan
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September 2nd, 2019 15:00
@Nyxnight if you use an eGPU and connect to the display directly to it, then yes that would work, because in that case you WOULD have your display connected directly to the GPU you were trying to use. You don't need a dock in addition, and in fact having both might be more complicated anyway. If you want a docking station type of setup, look at eGPU enclosures like the Razer X Chroma that include built-in Ethernet and USB ports.