I am running Ubuntu 12.04.2 in dual boot with Windows 7 on the same drive.

In Windows, I customize my refresh rate for my 2nd monitor with the program powerstrip. When I export my Linux modeline and create a new mode for Ubuntu, I get the following errors when I try to change my 2nd monitor to that mode:

~$ xrandr --output DFP3 --mode "1400x1050_2" 
xrandr: Configure crtc 1 failed

My question is, how can I remedy this problem? I need to have the same custom timings as Wndows.

My specs are:

  • Ubuntu 12.04.2 (3.5.0-23-generic)

  • AMD driver catalyst-13.1-linux-x86.x86_64

  • P6x58D premium motherboard

  • 6 gigs of ram

  • 23 inch Asus monitor

  • 15 inch DIY monitor.


The following steps are needed to change the display mode using xrandr:

1. Get modeline

To change the geometry of an attached screen we first need to calculate the modeline for a desired resolution with gtf or cvt (whatever is installed):

cvt <xres> <yres> <refresh>

For a resolution of 1400x1050 at 50Hz this will give us the follwing modeline:

# 1400x1050 49.97 Hz (CVT 1.47M3) hsync: 54.11 kHz; pclk: 100.00 MHz
Modeline "1400x1050_50.00"  100.00  1400 1480 1624 1848  1050 1053 1057 1083 -hsync +vsync

2. Define new mode

Copy and paste the modeline to add it as a new mode named 1400x1050_50.0 (or any other name we choose) for xrandr:

 xrandr --newmode "1400x1050_50.00"  99.88  1400 1480 1624 1848  1050 1051 1054 1081  -HSync +Vsync

3. Attach mode to monitor

We then attach this new mode to our monitor, e.g. DFP3 (note that this will error if we had chosen a mode not supported by the graphics card driver):

xrandr --addmode DFP3 1400x1050_50.00

4. Change mode

After this was successful we then can switch to this new mode using

xrandr --output DFP3 --mode 1400x1050_50
  • Thank you for the reply. I should have mentioned that I already do the above steps. Everything goes fine until I change mode. That is when I get the error. Now, I know that my graphics card (HD5850) is able to get the mode in Windows, so I think it should work in Ubuntu as well. I believe that the problem may simply be because the drivers for linux are not good compared to Windows drivers.
    – ryanwc
    Mar 25 '13 at 3:48
  • Yeah, this is a driver issue then. Try to purge fglrx to test if the open radeon driver does better.
    – Takkat
    Mar 25 '13 at 7:02

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