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Ashers2001
Copper

UP2414Q, TB from PC, 6-bit color

I have a problem with the UP2414Q monitor, when using DP1.2 mode (i.e. 4K at 60Hz).  When I connect it via a DP in a laptop, it works correctly (other than the well reported sleep issues), with 8-bit color. See attached screenshots:

Capture.PNGConnected using MiniDP to DPCapture2.PNGConnected using miniDP to DP 

However, when I connect it using laptops that have only Thunderbolt, it recognizes the monitor as 6-bit color (see below screenshot), which causes color banding on the screen.  Does anyone know how to force Windows into recognizing that the monitor is 8-bit color?

2018-06-01.pngConnected using Thunderbolt to DP (Note the bit depth)

I have tried the following:

- Using two different computers which have different video cards (so it's not the driver)

- Using two different USB-C to DP cables

- Connecting the monitor using a DP to miniDP cable that I know works connected to a thunderbolt dock that supports 2x4K monitors at 60Hz.

- Installing the UP2414Q monitor driver.

In all cases, the monitor is showing as 6-bit when connected via Thunderbolt.  Note that it is even 6-bit color when I select a lower resolution (with DP1.2 on).  The only thing I can do to force 8-bit color is to turn off DP1.2 or connect via HDMI (but then, of course, I'm limited to 30Hz at 4K).

 

Any suggestions gratefully received.  Thanks!

 

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Moderator
Moderator

Re: UP2414Q, TB from PC, 6-bit color

 

The fact that when using DP the UP2414Q shows 8-bit color means that the UP2414Q hardware is OK.

The three pictures you presented list three different GPU =
Surface tablet Intel Iris 540
PC ? Intel HD 4600
PC ? Intel HD 620

That implies three systems, not two. Or did you mean two PC laptops plus the Surface tablet?

* What are the two laptop models?
* What operating system on both?


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Ashers2001
Copper

Re: UP2414Q, TB from PC, 6-bit color

Many thanks for the response.  I have tested the monitor with the following four systems:

  • Surface Pro 4 (Intel Iris 540) using miniDP port: works fine (8-bit color)
  • Dell XPS 15 9530 (Intel HD 4600) using miniDP port: works fine (8-bit color)
  • Lenovo Thinkpad X1 Yoga 3rd Gen (Intel HD 620) using thunderbolt port: banding (6-bit color)
  • Eve V i7-7Y75 (Intel HD 615) using thunderbolt port: banding (6-bit color) - screenshot was not included

All systems are running the latest Windows 10 Pro (version 1803). But it was the same problem with the previous Windows 10 release (1709).

Given the above, what seems be causing the 6-bit color is connecting the monitor to the laptop via thunderbolt.  I have tested using two different USB-C to DP cables (that support 4K-60Hz) and using an HP Thunderbolt Dock (which supports two 4K-60Hz monitors and has a DP port).  Therefore, I don't think it is a problem with the cable or connection to the monitor.

Note that it may be related to this issue:

https://www.dell.com/community/Monitors/U2717D-TB3-from-dock-mDP-to-DP-cable-6-bit/m-p/6089603

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Ashers2001
Copper

Re: UP2414Q, TB from PC, 6-bit color

@DELL-Chris M 

I was wondering whether you had any thoughts on this issue.  I'd be happy to provide further information to support.

Many thanks

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Moderator
Moderator

Re: UP2414Q, TB from PC, 6-bit color

 

We are not seeing this issue in our lab. But we are only testing on Dell PCs. The Dell monitor driver only installs the INF, CAT, and ICM so that the operating system can note it correctly. It does not control the source TB3 transmission. That is done via the source PC chipset driver and associated TB3 driver in the operating system. Based on your testing, the Lenovo ThinkPad X1 Yoga and Eve V need their chipset drivers updated, and possibly the TB3 driver if they supplied one on their websites.


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