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Ashers2001
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UP2414Q, TB from PC, 6-bit color

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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

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

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

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

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

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I have a Dell UP3214Q monitor and see the same issue with my new XPS 9570, who as an Intel UHD G630.
my old XPS (9530) with a Intel G4600) didn't have this issue. I have a Dell support ticket open, if we figure it out I'll let you know.

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

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8-bit color = Intel 4600/Iris 540
6-bit color = Intel 615/620/630

Has to be some Intel chipset or GPU driver fault?

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Ashers2001
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Re: UP2414Q, TB from PC, 6-bit color

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Many thanks for the responses.  I had suspected that it was sending the DP signal via Thunderbolt that was the problem (given it causes banding in all cases that I've seen), but it could be the Intel drivers as you suggest.

One way to check would be to test the UP2414Q or UP3214Q with the Dell Precision 7520 which has both Mini-DP and Thunderbolt.  If it produces 8-bit color at 4K 60Hz when using Thunderbolt and similarly when using miniDP, then that would point to the drivers.  I think that laptop also has Optimus, so the output may also be provided by the Intel graphics driver (rather than the nVidia), so that might also reveal some information.

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

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Hi. I have a similar issue to you and found that I could workaround it by rolling back to old Intel HD driver.

I listed a few driver versions on my thread that you can try. Please confirm if rolling back the driver fixes things for you as well.

Ashers2001
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Re: UP2414Q, TB from PC, 6-bit color

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@superparamagneticWell spotted!

I can confirm that, in my situation, rolling back to 22.20.16.4815 did work on my machine and I was able to get 8-bit color through Thunderbolt.  Unfortunately, the old driver didn't seem particularly stable on my machine, so I've had to revert back to the current driver.

So it is a driver problem.  Using more recent Intel drivers causes 6-bit color via Thunderbolt.

It would be great if Dell could work with Intel to get updated drivers that bring back 8-bit color via Thunderbolt.

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