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I am attempting to get a display resolution of 2560x1440 to operate correctly through DVI output on my Lenovo ThinkCentre M71e running Ubuntu 12.04. The computer has both VGA and DVI connectors.


When I use the VGA connector I get the full 2560x1440 resolution of my monitor just fine. Infact this is autodetected as the default resolution with no config on my part. The only issue is some ghosting in the image due to the analog connection.

The output of xrandr at this point is as follows:

 % xrandr
Screen 0: minimum 320 x 200, current 2560 x 1440, maximum 8192 x 8192
VGA1 connected 2560x1440+0+0 (normal left inverted right x axis y axis) 597mm x 336mm
   2560x1440      60.0*+
   1920x1080      60.0  
   1680x1050      74.9  
   1280x1024      75.0     60.0  
   1440x900       59.9  
   1152x864       75.0  
   1280x720       60.0  
   1024x768       75.1     60.0  
   800x600        72.2     75.0     60.3     56.2  
   640x480        75.0     60.0  
   720x400        70.1  
HDMI1 disconnected (normal left inverted right x axis y axis)
DP1 disconnected (normal left inverted right x axis y axis)

Note that X believes the computer has VGA, HDMI, and DP (DisplayPort?) connections. It infact has VGA and DVI.


When I use the DVI connector I get only 1680x1050 resolution, and xrandr reports the following:

 % xrandr
Screen 0: minimum 320 x 200, current 1680 x 1050, maximum 8192 x 8192
VGA1 disconnected (normal left inverted right x axis y axis)
HDMI1 connected 1680x1050+0+0 (normal left inverted right x axis y axis) 597mm x 336mm
   1680x1050      60.0* 
   1280x1024      75.0     60.0  
   1440x900       59.9  
   1152x864       75.0  
   1280x720       60.0  
   1024x768       75.1     60.0  
   800x600        72.2     75.0     60.3  
   640x480        75.0     60.0  
   720x400        70.1  
DP1 disconnected (normal left inverted right x axis y axis)

Note it believes to be connected over HDMI, not DVI.

I can try to force the correct resolution over DVI as shown below, but this simply results in a blank display.

 % gtf 2560 1440 60.0

  # 2560x1440 @ 60.00 Hz (GTF) hsync: 89.40 kHz; pclk: 311.83 MHz
  Modeline "2560x1440_60.00"  311.83  2560 2744 3024 3488  1440 1441 1444 1490  -HSync +Vsync

 % xrandr --newmode "2560x1440_60.00"  311.83  2560 2744 3024 3488  1440 1441 1444 1490  -HSync +Vsync 
 % xrandr --addmode HDMI1 2560x1440_60.00
 % xrandr --output HDMI1 --mode 2560x1440_60.00

Notes:


I have also tried using cvt instead of gtf to generate the new modeline. This results in a much lower pixel clock of 241.5MHz (matches exactly the maximum pixel clock value from display manual). Unfortunately the screen still turns blank when I try this.

 % cvt -r 2560 1440
# 2560x1440 59.95 Hz (CVT 3.69M9-R) hsync: 88.79 kHz; pclk: 241.50 MHz
Modeline "2560x1440R"  241.50  2560 2608 2640 2720  1440 1443 1448 1481 +hsync -vsync
 % xrandr --newmode "2560x1440R"  241.50  2560 2608 2640 2720  1440 1443 1448 1481 +hsync -vsync
 % xrandr --addmode HDMI1 2560x1440R
 % xrandr --output HDMI1 --mode 2560x1440R
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1  
Is the DVI connector on your motherboard, a dual-link capable connector? –  dobey Jan 31 at 17:39
    
@dobey I'm not sure. The website for the machine doesn't mention if the DVI port is dual link or not. shop.lenovo.com/us/desktops/thinkcentre/m-series/m71e –  pauldoo Jan 31 at 18:07
    
I have also tried installing the xserver backport from saucy (13.10). This didn't help. (sudo apt-get install xserver-xorg-lts-saucy) –  pauldoo Jan 31 at 18:08
    
Maybe call Lenovo support and ask for verification on whether that model supports dual-link DVI connections or not. If it does not, you'll need a discrete graphics card which does, to use that resolution on DVI. I'd also recommend trying the saucy HWE kernel if possible. There could be a kernel bug that has since been fixed in a newer kernel. –  dobey Jan 31 at 18:37

1 Answer 1

I found that aiming for 2560x1440 at 30Hz instead of 60Hz works just fine. This is consistent with @dobey's comments above that the DVI connection may only be single link. This is good enough for me (no gaming), and text is visibly sharper than with VGA.

I followed a Google+ post by Linus to get this working: https://plus.google.com/+LinusTorvalds/posts/HQsCY7ErAL4

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