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5 Posts

01-08-2019

Sweden

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  • Message 21 of 38

Re:ThinkPad USB-C Dock Gen2 and Dual monitor 2560×1440

2020-11-20, 14:16 PM

I am having this problem with USB-C Dock Gen 2 when I connect two ThinkVision T27h-20 (WQHD - max resolution 2560 x 1440) to an HP EliteBook 840 G5.

One of the monitor is working perfectly at 2560x1440, but the second one is limited on 1920x1080 and it's flickering like hell.

 

This is very strange because the same setup, it's working on my Thinkpad A485... 

 

All the drivers and dock firmware are updated to latest versions.

 

I followed all the solutions online. Does anyone knows how to fix this?

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1 Posts

01-25-2021

United States of America

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  • Message 22 of 38

Re:ThinkPad USB-C Dock Gen2 and Dual monitor 2560×1440

2021-01-25, 16:39 PM

Hello I have a T14 Laptop and a USB C Gen 2 dock, the video card is Intel

I am trying to use two monitors at WQHD (3440x1440) with DP...I only get one with the other being stuck at 1920x1080 and flickering

i have used all combos of HDMI to DP alternatives, switching cables slots etc.

 

I have read multiple threads that post similar questions to mine, or similar problems, but with different kinds of monitors similar outcome.

 

I found a compatibility scale from Lenovo that talks about DP 1.2 vs 1.4 but ain’t clear what I have , it also talks about specific laptop models with more compatibility using the AMD video card than the Intel video card, and my T14 is not listed under the models to support two monitor configuration under the Intel section

 

Can I use two monitors at full resolution 3440x1440 with a T14 Intel video card and a usb c gen 2 dock? 
please help

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572 Posts

06-26-2016

Germany

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  • Message 23 of 38

Re:ThinkPad USB-C Dock Gen2 and Dual monitor 2560×1440

2021-01-25, 17:42 PM

@ Harlock-qqq wrote:

Can I use two monitors at full resolution 3440x1440 with a T14 Intel video card and a usb c gen 2 dock? 
please help

 

the rule of thumb until recently was Intel = DP1.2.  With certain exceptions like the P14/P15/and several other P* workstation models with real discrete Nvidia GPUs.

Recently introduced Intel system with core i[579]-11***   processors   will also support DP1.4. Not sure about i3-11*** systems.

 

An Intel T14 system can drive only one 4K display at 30Hz attached to a USB-C gen2 dock.  You could try connecting each display directly to a USB-C port of the T14.

This might enable 4K @60Hz for both displays, but I'm not sure.   Using usb-c to usb-c cables introduces another obstacle you need to  be aware of.  If a monitor does have built-in USB3 ports, then you need to find a setting in OSD and limit speed of monitor's USB ports to USB2.  With USB3 available, the maximum video resolution is  again 4K  @30Hz.

Hope this helps.

 

Tech-Savvyness does not replace reading the fine manual.
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101 Posts

01-24-2019

United States of America

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  • Message 24 of 38

Re:ThinkPad USB-C Dock Gen2 and Dual monitor 2560×1440

2021-02-04, 22:31 PM

USB-C dock is the issue and DisplayPort 1.2. 

 

We had same issue. 

 

Solution: Purchase ThunderBolt 3 Dock. I have two 4K screens connected to my T14 Intel. My Resolution is 3840 x2160 for each 4K screen.  Laptop screen res is at 1920 x1080

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1 Posts

03-05-2021

Finland

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  • Message 25 of 38

Re:ThinkPad USB-C Dock Gen2 and Dual monitor 2560×1440

2021-03-05, 13:48 PM

Hi all!

 

My configuration:
Computer: ThinkPad T490 20N3

Monitors: 2x Lenovo ThinkVision P24q-20 | 2560 x 1440 WQHD

Dock: Thinkpad USB-C Dock Gen2

Cables: USB-C from computer to dock. Display cables from dock to monitors.

 

Problem: Only the first monitor was 2560x1440, the other didn't even have an option to 1920x1080.

So how I got 2560x1440 to both monitors. Not with this dock, I had to order ThinkPad Thunderbolt 3 G2 (check if you have Intel/AMD!) so that I can use 1 cable connection with my laptop and current monitors.

 

So yeah, my problem was my monitors. Lenovo ThinkVision P24q-20 monitor's displayport is 1.2 and if I understood correctly USB-C Dock Gen2 doesn't support 2 above fullhd monitors with DP1.2.

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572 Posts

06-26-2016

Germany

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  • Message 26 of 38

Re:ThinkPad USB-C Dock Gen2 and Dual monitor 2560×1440

2021-03-05, 15:12 PM

@ Ilkkapossu wrote:

So yeah, my problem was my monitors. Lenovo ThinkVision P24q-20 monitor' displayport is 1.2 and if I understood correctly USB-C Dock Gen2 doesn' support 2 above fullhd monitors with DP1.2.

 

The monitors are not the problem here. Displays  with DP1.4  would not change anything in  this setup. Important here is the DP  version agreed to  by T490 system and the dock and whether full DP data rate is available or not.

With both docking stations  it's DP1.2 because T490 supports DP1.2 only.  And the USB-C Gen dock limit's DP data rate to 50%. The Thunderbolt dock does not set any limit on DP data rate, because the TB link works differently than the ordinary USB-C link with USB3 and DP alt mode.

 

Tech-Savvyness does not replace reading the fine manual.
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6 Posts

03-09-2021

France

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  • Message 27 of 38

Re:ThinkPad USB-C Dock Gen2 and Dual monitor 2560×1440

2021-03-09, 9:13 AM

Hi,

My configuration :

Thinkpad T14 Gen 1 AMD Ryzen 7

Monitors : 2x Dell S2721DS 2560x1440 and 1x acer 1920x1080
Dock : ThinkPad USB-C Dock Gen2

 

On Linux I can connect only one monitor on the dock and 2 others monitors are connected directly on the laptop with hdmi and usb-c port.

If I connect the 2 2560x1440 monitors on the dock, one of them stay in standby

Before this configuration I was able to put 2 1920x1080 screens on the dock.

 

On Windows if I connect the 2 2560x1440 monitors on the dock with hdmi/DP all works.

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572 Posts

06-26-2016

Germany

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  • Message 28 of 38

Re:ThinkPad USB-C Dock Gen2 and Dual monitor 2560×1440

2021-03-09, 14:17 PM

@ Leven0 wrote:

 

Before this configuration I was able to put 2 1920x1080 screens on the dock.

 

It seems that the system is not enabling DP1.4,  May be a missing kernel quirk setting.  Two FHD displays are the limit for DP1.2 systems connected to a USB-C dock.

This explains, why you are able to connect/use  only one QHD display.

 

Have you tried booting a current up to-date linux live cd?

 

 

On Windows if I connect the 2 2560x1440 monitors on the dock with hdmi/DP all works.

Windows drivers have enabled DP1.4 HBR3 mode.

 

Tech-Savvyness does not replace reading the fine manual.
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6 Posts

03-09-2021

France

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  • Message 29 of 38

Re:ThinkPad USB-C Dock Gen2 and Dual monitor 2560×1440

2021-03-09, 14:48 PM
Yes I've try to boot on latest ubuntu live cd the last week. I'm currently on Ubuntu 20.10 and kernel version is 5.8.0-44-generic
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572 Posts

06-26-2016

Germany

1082 Signins

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  • Message 30 of 38

Re:ThinkPad USB-C Dock Gen2 and Dual monitor 2560×1440

2021-03-09, 16:04 PM

I guess you need to open an Ubuntu bug report.

 

Out of interest, could you please post  the dmesg log, especially  the lines where the dock and  gpu are reported?

 

and may be  also the output of   lsusblspci -knn   and xrandr

and lastly  the output  of    sudo find /sys/class/typec/ -ls

see  https://www.kernel.org/doc/html/latest/driver-api/usb/typec.html

 

maybe try  a Ubuntu  21.04  daily snapshot: 
http://cdimage.ubuntu.com/daily-live/current/

 

Tech-Savvyness does not replace reading the fine manual.
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