Low resolution in Debian

Question

I installed Debian 8.3 LXDE today and I cannot adjust the resolution of my monitor. I have a 1920x1080 resolution, but allows you to install Debian to me only 1280x1024. I tried to make as here: https://wiki.archlinux.org/index.php/xrandr, using xrandr to do manually, but there is no connected interfaces:

drahenfels@debian:~$ xrandr 
xrandr: Failed to get size of gamma for output default
Screen 0: minimum 640 x 400, current 1280 x 1024, maximum 1280 x 1024
default connected 1280x1024+0+0 0mm x 0mm
1280x1024      0.00* 
1152x864       0.00  
1024x768       0.00  
800x600        0.00  
640x480        0.00  
720x400        0.00 

My GPU: AMD/ATI RS780L [Radeon 3000]

Answer 1

Well the Arch Linux wiki is well detailed about this, so I think you've tried this... But anyway you could manually add the mode to your system or something like that.

Example: supposing I don't have the 1920x1080 resolution down here, my display name is VGA1, and yours try to see the name on your GUI display settings manager or arandr, but up there on your post it says 'default connected' so I guess the name might be that, "default" (That supposition because mine says "VGA1 connected..."), I might be wrong.

$ xrandr
Screen 0: minimum 8 x 8, current 1920 x 1080, maximum 32767 x 32767
VGA1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 510mm x 290mm
   1920x1080     60.00*+
   1280x1024     75.02    60.02  
   1152x864      75.00  
   1024x768      75.03    60.00  
   800x600       75.00    60.32  
   640x480       75.00    59.94  
   720x400       70.08  
VIRTUAL1 disconnected (normal left inverted right x axis y axis)

So to get the mode, I do

$ cvt 1920 1080
# 1920x1080 59.96 Hz (CVT 2.07M9) hsync: 67.16 kHz; pclk: 173.00 MHz
Modeline "1920x1080_60.00"  173.00  1920 2048 2248 2576  1080 1083 1088 1120 -hsync +vsync
$ 

Then copy all after Modeline to create new mode on xrandr

# xrandr --newmode "1920x1080_60.00"  173.00  1920 2048 2248 2576  1080 1083 1088 1120 -hsync +vsync

Add the newly created mode on your display

$ xrandr --addmode VGA1 1920x1080_60.00

Then apply it, you can use the GUI interface for that

$ xrandr -s 1920x1080_60.00            

Answer 2

You probably need some non-free firmware/driver for your video card. Read https://wiki.debian.org/AtiHowTo