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i'm trying to connect an external monitor to my Lenovo T420 using the DisplayPort but it's not working. If i connect it via VGA it works fine, but the image on the monitor is lacking sharpness and it's flickering (the cause of that I discovered to be some interference in the VGA output). So, I want to connect my external monitor using DisplayPort, but when i do so, i get no image on it. And when i run the xrandr command, I don't see any display port:

    $ xrandr
Screen 0: minimum 320 x 200, current 3520 x 1200, maximum 32767 x 32767
LVDS1 connected 1600x900+0+300 (normal left inverted right x axis y axis) 309mm x 174mm
   1600x900       60.0*+   40.0  
   1440x900       59.9  
   1360x768       59.8     60.0  
   1152x864       60.0  
   1024x768       60.0  
   800x600        60.3     56.2  
   640x480        59.9  
VGA1 connected 1920x1200+1600+0 (normal left inverted right x axis y axis) 518mm x 324mm
   1920x1200      60.0*+
   1920x1080      59.9  
   1600x1200      60.0  
   1680x1050      60.0  
   1280x1024      75.0     72.0     60.0  
   1440x900       75.0     59.9  
   1024x768       75.1     70.1     60.0  
   800x600        72.2     75.0     60.3  
   640x480        72.8     75.0     66.0     60.0  
   720x400    

70.1  

When running lspci -v i can see both my graphic cards:

00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09) (prog-if 00 [VGA controller])
    Subsystem: Lenovo Device 21d0
    Flags: bus master, fast devsel, latency 0, IRQ 46
    Memory at f1400000 (64-bit, non-prefetchable) [size=4M]
    Memory at e0000000 (64-bit, prefetchable) [size=256M]
    I/O ports at 6000 [size=64]
    Expansion ROM at <unassigned> [disabled]
    Capabilities: <access denied>
    Kernel driver in use: i915

....

01:00.0 VGA compatible controller: NVIDIA Corporation GF119M [Quadro NVS 4200M] (rev a1) (prog-if 00 [VGA controller])
    Subsystem: Lenovo Device 21d0
    Flags: fast devsel, IRQ 11
    Memory at f0000000 (32-bit, non-prefetchable) [disabled] [size=16M]
    Memory at c0000000 (64-bit, prefetchable) [disabled] [size=256M]
    Memory at d0000000 (64-bit, prefetchable) [disabled] [size=32M]
    I/O ports at 5000 [disabled] [size=128]
    Expansion ROM at f1000000 [disabled] [size=512K]
    Capabilities: <access denied>

In Bios my settings are "Discrete Graphics" and OS detection Disabled. Any idea what i could do to make the display port work?

I'm running Ubuntu 13.04.

Thanks!

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