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P2415Q, TB16, XPS 15-9560, 6-bit color
When I connect the P2415Q using either the DP or mDP on the TB16, the P2415Q shows up as 6-bit bit depth in Windows Advanced Display Settings, and results in noticeable banding in smooth gradient regions.
This does not occur when using a USB Type-C to DP adapter connected either directly to the XPS 15-9560 TB3 port or to the TB16 TB3 port, and the P2415Q connects fine at 8-bit bpc, which looks normal. However this robs me of the only USB Type-C port available.
Hard resetting and factory resetting the P2415Q does nothing. However, I found that rolling back the Intel HD 630 drivers to before December 2017 fixes the issue. I did so by uninstalling the current driver in device manager and installing the old one from Dell's website.
I also tried several other drivers, in particular:
21.20.16.4664,A04 (Dell): 8-bit normal
22.20.16.4815 (Windows): 8-bit normal
23.20.16.4973 ,A06 (Dell): 6-bit banding
24.20.100.6194 (Intel): 6-bit banding
This also appears to be related to a few other issues:
https://www.dell.com/community/Monitors/UP2414Q-TB-from-PC-6-bit-color/m-p/6089105#M115779
https://www.dell.com/community/Monitors/U2717D-TB3-from-dock-mDP-to-DP-cable-6-bit/m-p/6089603
https://www.dell.com/community/Monitors/U2518D-MST-2nd-showing-as-6-bit/m-p/6075105
https://www.dell.com/community/XPS/XPS-13-9350-external-dell-monitor-banding-issues/td-p/5713532
https://communities.intel.com/thread/125232
It seems that some time around December 2017, Intel introduced drivers that broke compatibility with this monitor and other Dell monitors under certain circumstances. While I have workarounds for now, neither are really acceptable long term solutions. Please escalate this issue to your engineering teams so that they can work with Intel to fix this.
DELL-Chris M
Community Manager
Community Manager
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54.9K Posts
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August 3rd, 2018 07:00
Great that you figured out that the Intel HD 630 driver was the culprit and that the hardware is OK. Will notify the Displays and Drivers Team.
This is how you should be setup, correct?
TB16 TB3/USB Type-C cable --> XPS 15-9560 left side TB/USB 3.1 Gen 2/Type-C port
TB16 DP out port --> P2415Q DP to mDP cable --> P2415Q mDP in port
-or-
TB16 mDP out port --> P2415Q mDP to DP cable --> P2415Q DP in port
-or-
TB16 DP out port --> retail DP to DP cable --> P2415Q DP in port
-or-
TB16 mDP out port --> retail mDP to mDP cable --> P2415Q mDP in port
This is confusing to me =
This does not occur when using a USB Type-C to DP adapter connected either directly to the XPS 15-9560 TB3 port or to the TB16 TB3 port, and the P2415Q connects fine at 8-bit bpc, which looks normal. However this robs me of the only USB Type-C port available.
Are these the setups?
XPS 15-9560 left side TB/USB 3.1 Gen 2/Type-C port --> USB Type-C to DP adapter --> P2415Q DP to mDP cable --> P2415Q mDP in port
TB16 TB3/USB Type-C cable --> USB Type-C to DP adapter --> P2415Q DP to mDP cable --> P2415Q mDP in port
superparamagnetic
8 Posts
0
August 3rd, 2018 09:00
Yes I believe that is correct.
I'll do some simpler diagrams just to confirm we're on the same page.
Affected by driver:
XPS9560 --> TB16 --> mDP to DP --> P2415Q
XPS9560 --> TB16 --> DP to mDP --> P2415Q
XPS9560 --> TB16 --> DP to DP --> P2415Q
Not affected:
XPS9560 --> USBC/DP adapter --> DP to mDP --> P2415Q
XPS9560 --> TB16 --> USBC/DP adapter --> DP to mDP --> P2415Q
I also tried the HDMI outputs on either the XPS9560 or the TB16 which were also unaffected but were of course limited to 30Hz.
Ashers2001
8 Posts
0
August 8th, 2018 06:00
I just wanted to confirm that I have precisely the same issue as superparamagnetic, as I've stated here:
https://www.dell.com/community/Monitors/UP2414Q-TB-from-PC-6-bit-color/m-p/6129442
Many thanks for discovering what the problem is, and finding a workaround. Let's hope that the driver can be fixed soon.
eraser17
4 Posts
0
August 9th, 2018 00:00
I can confirm that downgrading to the old Intel Driver fixes the problem in my case. I have 8-bit-color now.
I am using the Dell U2717D monitor with mDP in combination with Lenovo's Thunderbolt Dock.
This 15.46 driver I am using now is that one here (August 2017):
Before I was using a version from March 2018.
Please keep us updated about the status.
Thanks!
AlexKrois
2 Posts
0
August 9th, 2018 01:00
Can confirm, that this is the only solution that works (atleast for me)
eraser17
4 Posts
0
August 9th, 2018 01:00
Related issue:
https://www.dell.com/community/Monitors/UP2414Q-TB-from-PC-6-bit-color/m-p/6106467/highlight/false#M116171
betaloid
1 Message
0
November 2nd, 2018 10:00
superparamagnetic
8 Posts
0
November 9th, 2018 21:00
For anyone following this, there is a thread at Intel tracking the issue: https://communities.intel.com/thread/120305
It sounds like Intel will release a fix within the next month or so, and hopefully Dell will follow suit shortly after.
ChristopherDButler
22 Posts
0
November 15th, 2018 18:00
OMG what a nightmare this has been. 7 replacements between the 7710 and 7720 series mobile workstations, 2 TB 15 replacements then another two replaced out with TB16. Two P2715Q replacements, All for video and graphics related issues.
Everything was starting to work perfectly until this issue came up. Thank god I found this thread because I was not looking forward to any more hardware replacements.