Unsolved
4 Posts
1
3619
U2717D, TB3 from dock, mDP to DP cable, 6-bit
I purchased a brand new Dell U2717D monitor for use with a Thunderbolt 3 X1 carbon docking station. What I found is that when I connect using the supplied mini display or full display size display port cable, the color bit depth (Advanced display settings) is defaulted to 6-bit which is causing the banding. The only work around I have found is to use an HDMI cable which produces the full 8-bit color depth. While this works, I purchased this monitor for use with display port. What is interesting is that I also have a Dell U2715H monitor lying around and that DOES NOT have this issue and connects at an 8-bit color depth as one would expect. Both of these monitors use a 2560 x 1440 resolution. For me, doing a factory reset and toggling the MST setting has not made a difference. I will call Dell but I am not hopeful on a resolution given the relatively niche setup.
DELL-Chris M
Community Manager
Community Manager
•
54.3K Posts
0
June 2nd, 2018 07:00
I wonder if the fault could be with our mDP to DP cable? Maybe it would be worth testing an actual TB3/USB-C to DP cable?
Gevaudan
4 Posts
0
June 2nd, 2018 14:00
This is a good suggestion. I wish I had one of these cables lying around but unfortunately I do not.
I'm assuming that the TB3/USB-C end would connect to the dock and the full size DP end to the monitor. My dock is here: https://support.lenovo.com/us/en/solutions/acc100356
I did attempt to rule out the mDP to DP cable by using a full size DP to DP cable but the same issue exists there.
DELL-Chris M
Community Manager
Community Manager
•
54.3K Posts
0
June 3rd, 2018 11:00
Correct. I see the TB3/USB-C port right of the HDMI port. I did a search in the dock User's Guide for "bit". It does not mention 6-bit or 8-bit. Might be good to post the issue on the Lenovo Forum to see if other users had seen the 6-bit/8-bit issue.
Gevaudan
4 Posts
0
June 3rd, 2018 20:00
Good idea. I posted on Lenovo forum and am linking here for the benefit of others.
swamped207
425 Posts
0
June 4th, 2018 09:00
FWIW, I have one of those Thinkpad docks but don't see any problem with a UP2716D or UP2516D using either of the DP inputs on the dock, or chaining both off either DP input.
DELL-Chris M
Community Manager
Community Manager
•
54.3K Posts
0
June 4th, 2018 11:00
FWIW, I have one of those Thinkpad docks but don't see any problem with a UP2716D or UP2516D using either of the DP inputs on the dock, or chaining both off either DP input.
Using the Dell DP to mDP cable you always see 8-bit? What operating system?
Gevaudan
4 Posts
0
June 4th, 2018 20:00
In light of this new information, I did attempt to re-install Windows 10 to see if there was something specific to my installation (settings, drivers, etc) but alas no luck. It is interesting that the issue is only noticeable in Windows 10 -- not seeing it in Ubuntu (or at least I'm not noticing it there).
swamped207
425 Posts
0
June 5th, 2018 16:00
If by "seeing 8-bit" you mean the absence of notable banding, then Yes. But what I really meant was I see (under Win10) no difference between PC>monitor and PC>TB-dock>monitor. The actual connection links may matter here since I - similar, I think, to the OP - am connecting an Intel HD620 with Thunderbolt 3 (from Lenovo) to a USB-C-to-DP adapter (from CableMatters) to the mDP input on an 8-bit P3418HW panel, and then comparing it to the HD620 connected to a Lenovo TB3 dock, which in turn is connected to the same mDP input on the P3418 using the same Dell DP-to-mDP cable.
(AFAIK, there is no way for the system or system software to know the panel bit depth at the other end of the signal cable, so its not clear to me what the OP means by "the color bit depth (Advanced display settings) is defaulted to 6-bit which is causing the banding". I probably misunderstood or missed something here.)