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How-to display two external monitors on T420 via Dock+laptop VGA ?

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elfi
Posts: 5
Joined: Sun Jan 28, 2018 10:21 am
Location: Paris, France

How-to display two external monitors on T420 via Dock+laptop VGA ?

#1 Post by elfi » Sun Jan 28, 2018 10:46 am

Hello,

I own a great T420 Thinkpad (Intel HD3000 Graphics) with a dock, and it runs on Lubuntu 16.04. I am currently trying to use it with two external screens via two VGA sockets (one VGA socket from my laptop, the other one from my dock). I do not wish displaying the laptop screen.

Alas, at now, the two external screens are unable to display simultaneously.

When I only plug in the dock VGA cable, everything is fine. xrandr tells me :

Code: Select all

LVDS1 connected
VGA1 connected
When in addition I plug in the laptop VGA cable, the first dock-VGA-screen does not connect any more and the laptop-VGA-screen displays a distorted image (in fact, it has a different screen resolution). Then, xrandr tells me :

Code: Select all

LVDS1 connected [same outputvalues as before]
VGA1 connected [different output values : selected screen definition is same, but other possible screen definitions are different]
How can I use my two external screens simultaneously ? How-to then adapt my second external screen definition ?

Thanks for helping !

elfi

axur-delmeria
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Re: How-to display two external monitors on T420 via Dock+laptop VGA ?

#2 Post by axur-delmeria » Sun Jan 28, 2018 11:40 am

The VGA port on the dock is just a passthrough for the laptop's VGA port. Therefore you cannot use both at the same time.

You need to use the other outputs (Displayport on the laptop and/or dock, DVI on the dock). If both your monitors only have VGA inputs, then you need to use a Displayport to VGA converter.
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elfi
Posts: 5
Joined: Sun Jan 28, 2018 10:21 am
Location: Paris, France

Re: How-to display two external monitors on T420 via Dock+laptop VGA ?

#3 Post by elfi » Sun Jan 28, 2018 3:32 pm

This is bad news : there is no solution other than buying the DisplayPort-VGA cable…
Thank you very much for your reply !

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