Getting 5K on Linux


#1

I’ve just for a Plugable TB3 to Dual Displayport adapter for my Precision 5510 + Dell UP2715K monitor. On Windows, I get 5K, but the monitor seems to turn off every few minutes for 1-2 seconds before coming back on. On Linux, it seems to find two external monitors for the Dell 2715K - one 4K, and another one with a weird 848x480 or 2560x2880 resolution (from xrandr output). I’m not very experienced in setting up xorg / xrandr / etc., but is there a way to get 5K output instead of 4K? I’m running Ubuntu 16.10 with the 4.8.1 kernel.


#2

Hello and thanks for posting!

Just one quick note up front, while Plugable officially supports Linux on many of our products we do not offer official support for Linux with our Thunderbolt 3 adapters. We will do our best to help of course, but we like to set honest expectations up front.

To the behavior of the adapter while running Windows, we have seen behavior similar to what you describe with certain Dell Thunderbolt 3/USB-C systems like your Precision and we speak to those here -> http://plugable.com/2016/06/30/invest…

That post is long (although I would encourage you to read it in its entirety, including the comments) but the take away is that the problem appears to be internal to the Dell system itself. As a first step to see if we can improve the behavior, we need to ensure your system has the latest System BIOS, Thunderbolt driver, Thunderbolt NVM firmware, GPU driver. Once all the updates are applied, the next step is to lower the transmit power of the internal Wi-Fi adapter to 75% as described here -> http://plugable.com/2016/06/30/invest…I have made a list of the updates for your system below if you need them, please apply them in the order presented.

  1. BIOS -> http://www.dell.com/support/home/us/e…

  2. TB3 Driver -> http://www.dell.com/support/home/us/e…

  3. TB3 NVM firmware -> http://www.dell.com/support/home/us/e…

  4. Intel GPU -> http://www.dell.com/support/home/us/e…

  5. nVIDIA Quadro M1000M GPU (if your system has it, please double-check before applying) -> http://www.dell.com/support/home/us/e…

Once all those steps are complete, please test the adapter again while running Windows. If that helps, great! If not, please try lowering the Wi-Fi transmit power further. If still no result, please enable ‘Airplane Mode’ -> http://www.tenforums.com/tutorials/15… (which will disable the internal Wi-Fi adapter completely) and test again.

Let us know if that helps with things on the Windows side when you have a moment, and we will determine the next steps from there.

Thank you in advance for your patience!

Bob
Plugable Technologies
www.plugable.com/support


#3

Thanks for your response.

Updates:

I have two Precision 5510s. One was bought last December, the other in April. The one bought in April is running fine in Windows @5K. The December one is flashing badly. Both have the latest BIOS, firmware, and drivers installed. Airplane mode, disabling the intel wireless, and setting the Transmit Power to 3 (out of 5) - my Advanced window didn’t have “Power Output”, and that seemed the nearest - hasn’t helped one bit.

There are two differences between the two Precisions: The December one has 32GB of G.Skill Ripjaws DDR4 2666MHz ram, while the April one has 32GB of whatever RAM Dell shipped. Also, the former is running Windows 10 Anniversary Update with Fastring, and the second is running Windows 10 Anniversary Edition (not on fastring).

In terms of Linux, I would very much like to get it working. The frustrating thing is that Ubuntu sees that there are three monitors - the internal 4k, but sees the external as a 4K and a third low res one when using nvidia graphics with bumblebee. When forcing Prime (i.e. discrete nvidia only), it’s the same.


#4

Thanks for getting back, appreciate the extra details.

That the adapter is working properly on the 5510 purchased in April using Windows is a good sign. That lets us know that the Plugable adapter itself is working properly.

That the adapter is not working as expected with the 5510 purchased in December even with all the latest updates and disabling the internal Wi-Fi may point to an internal system problem. In previous cases helping other customers with the XPS and Precision, some have resorted to having Dell replace the system (in one case twice) to have things work as expected.

You mention that the December unit differs in the type of RAM installed. While I would not expect this to be affecting the behavior of the Plugable adapter, one way to rule that out would be to temporarily swap the RAM between the two units to see if the behavior changes.

To the Linux behavior (assuming this is on the April 5510 unit), does the behavior change when you disable the Nvidia GPU and only use the integrated Intel GPU?

Thank you,

Bob


#5

Hi Bob,
I’ve contacted Dell, and they’ll likely replace the faulty Precision.

As for Linux, yeah…regardless of driver, it sees three screens by default. I don’t know how to tell it that two of the screens is in fact one 5K screen.


#6

Thanks for getting back. Glad to hear Dell is going to replace the system.

To the Linux issue, while we won’t be able to help directly we should be able to point you in the right direction. This post -> https://devtalk.nvidia.com/default/to… while not offering a direct solution does indicate you are not alone.

Going a little deeper it may be that using Xinerama may be able to help, but the documentation is somewhat scattered and reports of success vary. I did find two references that may prove useful:

https://help.ubuntu.com/community/Xin…

https://wiki.archlinux.org/index.php/…

Thank you,

Bob


#7