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dauerbaustelle

Member

Registered: 2010-02-07

Posts: 62

Can't select external monitor's resolution using xrandr

An external monitor connected to my laptop can't be configured using xrandr to use its native resolution (1680x1050). I'm only offered 1024x768 and below (4:3 resolutions only).

I already tried using xrandr --addmode/--newmode but it doesn't work (--addmode: only changes the viewport size but not the resolution on the monitor --> viewport is cropped; --newmode: xrandr doesn't find the newly created mode).

I also tried the xorg.conf way (using PreferredResolution on the external screen) but startx seems to ignore xorg.conf entirely. Here's the xorg.conf I used: http://paste.pocoo.org/show/6t3rXGb8RPskuQdFIw6E/.

Any ideas what could be going wrong?

gorky

Member

From: Kraków, Poland

Registered: 2010-07-05

Posts: 96

Re: Can't select external monitor's resolution using xrandr

Start by deleting/renaming xorg.conf and writing what options in xrandr are you exactly using to configure both screens. Also the output of 'xrandr -q' might be helpful.

Last edited by gorky (2011-11-15 14:22:48)

dauerbaustelle

Member

Registered: 2010-02-07

Posts: 62

Re: Can't select external monitor's resolution using xrandr

Screen 0: minimum 320 x 200, current 1280 x 800, maximum 8192 x 8192
LVDS1 connected 1280x800+0+0 (normal left inverted right x axis y axis) 261mm x 163mm
   1280x800       60.0*+   50.0  
   1024x768       60.0  
   800x600        60.3     56.2  
   640x480        59.9  
VGA1 connected (normal left inverted right x axis y axis)
   1024x768       60.0  
   800x600        60.3     56.2  
   848x480        60.0  
   640x480        59.9  
HDMI1 disconnected (normal left inverted right x axis y axis)
DP1 disconnected (normal left inverted right x axis y axis)

(without xorg.conf)

I'd like to use

xrandr --output VGA1 --mode 1680x1050

but of course that's not available :-(

gorky

Member

From: Kraków, Poland

Registered: 2010-07-05

Posts: 96

Re: Can't select external monitor's resolution using xrandr

Does it work in 1680x1050 on any other system (Windows, MacOS) when connected by VGA? Because this is quite an insane resolution for analog cable and the monitor might be simply unable to handle this... It also seems that no info about the monitor is reported back to RandR...

First thing to check is the VGA cable, or the adapter (if any is used).
Maybe you could try connecting it via HDMI? HDMI2DVI interface is very simple and cheap and the quality will be FAR better.

Last edited by gorky (2011-11-15 18:25:25)

R00KIE

Forum Fellow

From: Between a computer and a chair

Registered: 2008-09-14

Posts: 4,734

Re: Can't select external monitor's resolution using xrandr

The sequence should be:

xrandr --newmode
xrandr --addmode VGA1
xrandr --output VGA1 --mode

I don't know about 1680x1050 but 1280x1024@75Hz works for me on what seems to be a similar setup.

---

R00KIE
Tm90aGluZyB0byBzZWUgaGVyZSwgbW92ZSBhbG9uZy4K

dauerbaustelle

Member

Registered: 2010-02-07

Posts: 62

Re: Can't select external monitor's resolution using xrandr

The machine doesn't have anything but a VGA out (despite the stuff XRandR displays).

I tried with 1280x800:

xrandr --addmode VGA1 1280x800
xrandr --output VGA1 --mode 1280x800

but that doesn't work either (it seems like the external monitor doesn't know of the changed resolution, only the viewport is made bigger --> viewport is cropped).

gorky

Member

From: Kraków, Poland

Registered: 2010-07-05

Posts: 96

Re: Can't select external monitor's resolution using xrandr

The machine doesn't have anything but a VGA out (despite the stuff XRandR displays).

This may be a real problem, as 1680x1050 pushed through VGA will almost certainly be fuzzy/blurry.

Neverthless, the suspicious thing is the physical connection. As I wrote before - check cable and adapter (if used).

Last edited by gorky (2011-11-16 09:54:52)

R00KIE

Forum Fellow

From: Between a computer and a chair

Registered: 2008-09-14

Posts: 4,734

Re: Can't select external monitor's resolution using xrandr

The machine doesn't have anything but a VGA out (despite the stuff XRandR displays).

I tried with 1280x800:

xrandr --addmode VGA1 1280x800
xrandr --output VGA1 --mode 1280x800

but that doesn't work either (it seems like the external monitor doesn't know of the changed resolution, only the viewport is made bigger --> viewport is cropped).

It would help if you posted all the commands you used and the output of xrandr (maybe from start until the end), maybe someone could spot the problem.

---

R00KIE
Tm90aGluZyB0byBzZWUgaGVyZSwgbW92ZSBhbG9uZy4K

gorky

Member

From: Kraków, Poland

Registered: 2010-07-05

Posts: 96

Re: Can't select external monitor's resolution using xrandr

It would help if you posted all the commands you used and the output of xrandr (maybe from start until the end), maybe someone could spot the problem.

In the second post there is an output of 'xrandr -q', where it can be seen that monitor's native resolution is not detected - it may be either faulty cable/adapter or monitor is not able to communicate via VGA.
Without checking cables and/or trying to use it on another O/S we would not proceed, adding modes to RandR won't solve the main problem.

Last edited by gorky (2011-11-16 13:45:36)

dauerbaustelle

Member

Registered: 2010-02-07

Posts: 62

Re: Can't select external monitor's resolution using xrandr

It works using Windows 7 (even with 1680x1050). I'll post the full xrandr output later.

dauerbaustelle

Member

Registered: 2010-02-07

Posts: 62

Re: Can't select external monitor's resolution using xrandr

Weird stuff -- it seems to work only if I plug in the monitor when X is already running... but surely that's just a matter of configuration. I'll get back to this thread if I'm stuck, thanks everyone so far!