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Kaktus317
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Registered: ‎04-28-2019
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Message 1 of 9

ThinkPad 490s Display Problems with Docking USB-C Gen 2

Hi,

 

I posted this in German already, but hope to have a larger scope with an English request as well:

I just got a ThinkPad T490s with a Docking USB-C Gen2 and I would like to use two external monitors with that. One is a Samsung U28ED590 (4k) and one an older Dell U2312 (Full HD). This does not work. The docking station is supposed to support 2x 4k. Under the windows display options I am only able to choosed 2x 1920x1080 for both monitors. There is no higher resolution option for an extended view. If I switch to "show only on display 1" I can choose the 4k for the Samsung display. When I use the extended view then, the Full HD monitor only gets 800x600 and I cannot choose something else (option is greyed out).

 

Since I am running out of ideas: any suggestions for me to try? Thanks in advance and best regards!

Community SuperMod
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Message 2 of 9

Re: ThinkPad 490s Display Problems with Docking USB-C Gen 2

Hi Kaktus317, and welcome to the Lenovo User Community!

 

Backing into this, the Docking Station Video Output matrix suggests your machine is a "2 Lanes HBR2* Source".

I don't work for Lenovo. I'm a crazy volunteer!
Kaktus317
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Message 3 of 9

Re: ThinkPad 490s Display Problems with Docking USB-C Gen 2

Hi,
well that does not make sense, since I was using a T450s before with another dock and connected the 4k via DP and FullHD via VGA just fine. Would be a hughe step down 4 generations down the road if this is not possible anymore.

 

EDIT:

Hmn, I was looking into this. Thanks for the tip! If I understand correctly DP1.2 leads to being a "2 Lanes HBR2 source" and since Lenovo is not using DP1.4 in 2019, but a technology of 2009, the docking station, which advertises to work with 2x 4k displays does not do this? So I would have a get another laptop with more than DP1.2 or another Docking Station (Thunderbold then?) to do this? Very confusing for the customer!

Lenovo Employee Shirleywu
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Message 4 of 9

Re: ThinkPad 490s Display Problems with Docking USB-C Gen 2

Dear Customer,

Welcome to Lenovo Community. We are sorry for confusing you.

As for USB-C Dock Gen2, there are two lanes for transferring DP signal.

DP Bandwidth is limited by systems' output relying on DP1.2 or DP1.4 supported of system's USB-C port which is connecting dock.

If dock connected to DP1.4 systems, 2 lanes@HBR3 provied by system,then dock can support 2*4K@30Hz display.

If dock connected to DP1.2 systems, 2 lanes@HBR2 provied by system,then dock can support 1*4K@30Hz display

T490s is  DP1.2 systems, so you can only set 1*4K@30Hz display, or two 1920*1080@60Hz display

Hope my explanation can help you 

Kaktus317
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Message 5 of 9

Re: ThinkPad 490s Display Problems with Docking USB-C Gen 2

Hi,

thanks for your reply. As you can tell from my post earlier I figured this out myself. But, is it so difficult to provide this information sound and clear on your product website(s)? It was very cumbersome to find the table about it and also to figure out the DP Version of the notebook! Also: Thunderbird Dock not working at first. Only the information somewhere in the forum, that you have to speratley install an intel driver for it. Seriously? Even for non techy customers this is just awfull support from your side!

 

EDIT: I still have serious issues with the two devices working together btw.: https://forums.lenovo.com/t5/ThinkPad-T400-T500-and-newer-T/ThinkPad-490s-Display-Problems-with-Dock...

 

MrHeidenBerg
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Message 6 of 9

Re: ThinkPad 490s Display Problems with Docking USB-C Gen 2

Shirleywu,
I have a T470 with the same issue.
But monitor 1 supports 2560x1440 and monitor 2 supports 1920x1080.

It is very confusing - I have just bought the USB-C Dock Gen 2 beliving it would support 2 x 2560x1440.
Roope
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Message 7 of 9

Re: ThinkPad 490s Display Problems with Docking USB-C Gen 2

Just came to say that I made the same mistake and nothing has been done about the info about this. I wanted to use one 4k@60Hz, but didn't realize that gen 2 dock requires dp 1.4 to do this for some reason? I'd be nice to know why 1.2 is not enough when 1.2 supports 4k@60Hz
aUserHasNoName
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Message 8 of 9

Re: ThinkPad 490s Display Problems with Docking USB-C Gen 2

 

it's quite simple. You get full DP1.2 bandwith if  a display is connected to a USB-C port. All 4 lanes are available just for DP.

With the USB-C dock you also want to transfer USB data + ethernet (usb to ethernet adapter  etc). In this case you get only 2 lanes dedicated for DP, the other 2 lanes are used for USB data. You get only 50% of the full DP1.2 bandwidth.

 

https://www.ti.com/lit/wp/slly021/slly021.pdf

 

 

Roope
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Message 9 of 9

Re: ThinkPad 490s Display Problems with Docking USB-C Gen 2

Thanks for clearing that up. I still think that its ridiculous that the consumer is supposed to know all that. Especially since in all stores it just says "Supports 4k@60Hz, compatible with X1..."

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