Precision Mobile Workstations

Last reply by 11-24-2020 Solved
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Can't get external monitor to use dedicated graphics card ?

Hello!

I have an issue running the external monitor off my laptop.

The laptop has a graphics card that is made for CAD work. But when I attached the second monitor, it used the very weak onboard graphic card instead of the CAD graphics card. I have tried turning the inboard graphics card off, but then I can not use the second monitor. So it looks like it only uses the onboard GPU for the external monitor?

Is there a way I can tell the laptop to use the CAD graphics card for the external monitor?

Here is a list of the graphics cards:
Onboard graphics: Intel HD Graphics 630
GPU: Nvidia Quadro M1200

Laptop: Dell Precision 5520

The laptop is connected to a Dell Thunderbolt Dock (TB16), from there I use a DisplayPort cable to connect to the monitor.

P.S. I have set the GPU to run the CAD software.

Many thanks!!

@jphughan 

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7 Thorium

@lksjjdhlkjcnv  The Precision 5500 Series systems are the sister systems of the XPS 15 models. On both systems, the discrete GPU is not directly wired to any display output, not even the one for the built-in display.  Instead, it operates as a render-only device when needed, passing completed video frames to the Intel GPU for output to displays.  This technology is called NVIDIA Optimus.  And this is why you can't completely disable the Intel GPU without losing video output.  It's also why you can't have the NVIDIA GPU directly control external displays, because this is a hardware wiring design issue.  There are some systems like the Precision 7000 Series models that have a BIOS option allowing you to choose which GPU controls the built-in display and the display outputs, but those systems have a more complex motherboard design that allows them to offer that flexibility.

The TB16 dock taps into the GPU outputs wired to the system's USB-C/TB3 output.  Those are controlled by the Intel GPU.  But again, that's true of the built-in display as well.  So if your CAD software behaves properly when you're only using the built-in display, I'm not sure why it would stop working properly when you attach an external display.  I know that there are some applications that still don't work with NVIDIA Optimus technology very well, even though it has been around for years now and is the most common design on dual GPU systems these days, but if this was an application compatibility issue, I wouldn't expect it to work on the internal display but not the external display.

In terms of possible fixes, if you've already opened NVIDIA Control Panel to configure the system to prefer the NVIDIA GPU for that application, the only other things I can think of at the moment would be to get the latest NVIDIA drivers directly from NVIDIA rather than Dell in case any Optimus bugs or application incompatibilities have been resolved, and then perhaps reach out to your CAD software vendor.


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7 Thorium

@lksjjdhlkjcnv  The Precision 5500 Series systems are the sister systems of the XPS 15 models. On both systems, the discrete GPU is not directly wired to any display output, not even the one for the built-in display.  Instead, it operates as a render-only device when needed, passing completed video frames to the Intel GPU for output to displays.  This technology is called NVIDIA Optimus.  And this is why you can't completely disable the Intel GPU without losing video output.  It's also why you can't have the NVIDIA GPU directly control external displays, because this is a hardware wiring design issue.  There are some systems like the Precision 7000 Series models that have a BIOS option allowing you to choose which GPU controls the built-in display and the display outputs, but those systems have a more complex motherboard design that allows them to offer that flexibility.

The TB16 dock taps into the GPU outputs wired to the system's USB-C/TB3 output.  Those are controlled by the Intel GPU.  But again, that's true of the built-in display as well.  So if your CAD software behaves properly when you're only using the built-in display, I'm not sure why it would stop working properly when you attach an external display.  I know that there are some applications that still don't work with NVIDIA Optimus technology very well, even though it has been around for years now and is the most common design on dual GPU systems these days, but if this was an application compatibility issue, I wouldn't expect it to work on the internal display but not the external display.

In terms of possible fixes, if you've already opened NVIDIA Control Panel to configure the system to prefer the NVIDIA GPU for that application, the only other things I can think of at the moment would be to get the latest NVIDIA drivers directly from NVIDIA rather than Dell in case any Optimus bugs or application incompatibilities have been resolved, and then perhaps reach out to your CAD software vendor.


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