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arew264

Member

From: Friendswood, Texas, US

Registered: 2006-07-01

Posts: 394

Website

[SOLVED] External Monitor Resolution - XRandR Fun

The basic problem is this: my laptop is connected to an external monitor that runs at 1280x1024 natively. My laptop only seems to want to run it at 1024x768.
My laptop screen runs at 1280x800 normally, so I initially thought that it might not even be able to run the external monitor at that resolution, but xrandr says this:

$ xrandr
Screen 0: minimum 320 x 200, current 1024 x 768, maximum 1280 x 1200
VGA-0 connected 1024x768+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
   1024x768       60.0* 
   800x600        60.3  
   640x480        59.9  
LVDS connected 1024x768+0+0 (normal left inverted right x axis y axis) 330mm x 210mm
   1280x800       60.1 +
   1280x720       59.9  
   1152x768       59.8  
   1024x768       59.9* 
   800x600        59.9  
   640x480        59.4  
S-video disconnected (normal left inverted right x axis y axis)

The maximum looks to be 1280x1200. Does this mean that I can run my external monitor at 1280x1024? Do I need to disable the laptop monitor somehow?

Following instructions from an Ubuntu forum, I used `gtf` to generate a ModeLine for the external monitor like this:

$ gtf 1280 1024 60

  # 1280x1024 @ 60.00 Hz (GTF) hsync: 63.60 kHz; pclk: 108.88 MHz
  Modeline "1280x1024_60.00"  108.88  1280 1360 1496 1712  1024 1025 1028 1060  -HSync +Vsync

I then added it to xrandr like this:

$ xrandr --newmode "1280x1024_60.00"  108.88  1280 1360 1496 1712  1024 1025 1028 1060  -HSync +Vsync

What's weird is that the xrandr output then changed to this:

$ xrandr
Screen 0: minimum 320 x 200, current 1024 x 768, maximum 1280 x 1200
VGA-0 connected 1024x768+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
   1024x768       60.0* 
   800x600        60.3  
   640x480        59.9  
LVDS connected 1024x768+0+0 (normal left inverted right x axis y axis) 330mm x 210mm
   1280x800       60.1 +
   1280x720       59.9  
   1152x768       59.8  
   1024x768       59.9* 
   800x600        59.9  
   640x480        59.4  
S-video disconnected (normal left inverted right x axis y axis)
  1280x1024_60.00 (0x98)  108.9MHz
        h: width  1280 start 1360 end 1496 total 1712 skew    0 clock   63.6KHz
        v: height 1024 start 1025 end 1028 total 1060           clock   60.0Hz

Did it just add that mode to the S-Video output? I can't set the external monitor (VGA-0) to that mode. The error looks like this:

$ xrandr --output VGA-0 --mode 1280x1024_60.00
xrandr: cannot find mode 1280x1024_60.00

What do I need to do to get my external monitor to run at 1280x1024? Is it even possible? My graphics card is an ATI XPress 200M (it's integrated). Should I give it more RAM? I'm using the open source "radeon" driver, and everything is up to date.

Last edited by arew264 (2009-06-09 22:04:19)

arew264

Member

From: Friendswood, Texas, US

Registered: 2006-07-01

Posts: 394

Website

Re: [SOLVED] External Monitor Resolution - XRandR Fun

Almost as soon as I posted this, I looked somewhere else and did this:

$ xrandr --addmode VGA-0 1280x1024_60.00

And then I could do this:

$ xrandr --output VGA-0 --mode 1280x1024_60.00

So the whole process from start to finish looks like this:

$ gtf 1280 1024 60

  # 1280x1024 @ 60.00 Hz (GTF) hsync: 63.60 kHz; pclk: 108.88 MHz
  Modeline "1280x1024_60.00"  108.88  1280 1360 1496 1712  1024 1025 1028 1060  -HSync +Vsync

#copy everything after "Modeline"
$ xrandr --newmode "1280x1024_60.00"  108.88  1280 1360 1496 1712  1024 1025 1028 1060  -HSync +Vsync
$ xrandr --addmode VGA-0 1280x1024_60.00
$ xrandr --output VGA-0 --mode 1280x1024_60.00

theloz

Member

Registered: 2008-11-08

Posts: 3

Re: [SOLVED] External Monitor Resolution - XRandR Fun

Hi!!
First of all thanks for your tip, it was really helpful. I'm actually using a Samsung NC10, always struggling with monitor resolution on the external VGA.
I've applied your solution successfully with a little modification here it is:

loz ~  $  gtf 1280 1024 60

  # 1280x1024 @ 60.00 Hz (GTF) hsync: 63.60 kHz; pclk: 108.88 MHz
  Modeline "1280x1024_60.00"  108.88  1280 1360 1496 1712  1024 1025 1028 1060  -HSync +Vsync

then I goes like

xrandr --addmode VGA 1280x1024_60.00

xrandr --output VGA --mode 1280x1024_60.00

Essentially the same thing with "VGA" instead of "VGA-0" and now I have a wonderful external working monitor in full capacity