Subject: I can't get 1920x1080 resolution on my monitor: How find the name of
the output for a "default" setup? (New Jessie install)
Why does xrandr use the word "default" instead of something like VGA-0?
What is "xrandr: Failed to get size of gamma for output default" telling me--
is it a problem?
Background:
I've just made a new install of Jessie on a new machine (using an Asus M5A
78L-M USB3 motherboard). I am using the onboard graphics and a monitor with a
resolution (well, actually an LED TV) of up to 1920x1080. I have another
computer attached to the same monitor (now via a KVM switch) and it works fine
(the other computer is running Wheezy).
I did the install using the 64-bit AMD netinst.iso from a pendrive--that
worked "fine". (Update: I've since downloaded DVD-1 and made a new install
from there using the Advanced Graphical install method--it has made no
difference (with respect to screen resolution).
My problem is that the new computer only detected resolutions up to 1024x768
(see below).
I've done a fair amount of googling (and reading and experimenting, and will
keep doing that), but I wanted to ask some questions here.
One of the things I found were instructions on how to use cvt and xrandr to
create a modeline for 1920x1080 resolution, and then put that modeline to
use--so far I haven't been successful.
(Aside: I have used lspci and lsmod to confirm that the appropriate AMD driver
is being used.)
One problem is that I get a message: "xrandr: Failed to get size of gamma for
output default" every time I run xrandr. I've googled for that, and found
some pages that mention it, but none (so far) that really explained the cause
of the message or how to fix it.
Another problem is that I don't know the name of the xrandr output device. It
shows up as "default" and I've tried that, VGA1, and VGA-0, crtc 0, primary--
(with and without quotes) and none seem to work.
Any suggestions?
Here is a konsole session of one of my attempts to use cvt and xrandr to set
up a new mode (as stated above, I've also tried default, VGA1, VGA-1, VGA-0,
crtc 0, primary (with and without quotes) and none have worked.
Notice the 2nd last line which says: "xrandr: cannot find output "primary""
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rhk@s31:~$ 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
rhk@s31:~$ xrandr
xrandr: Failed to get size of gamma for output default
Screen 0: minimum 640 x 400, current 1024 x 768, maximum 1024 x 768
default connected primary 1024x768+0+0 0mm x 0mm
1024x768 0.00*
800x600 0.00
640x480 0.00
720x400 0.00
rhk@s31:~$ xrandr --newmode "1920x1080_60.00" 173.00 1920 2048 2248 2576
1080 1083 1088 1120 -hsync +vsync
xrandr: Failed to get size of gamma for output default
rhk@s31:~$ xrandr
xrandr: Failed to get size of gamma for output default
Screen 0: minimum 640 x 400, current 1024 x 768, maximum 1024 x 768
default connected primary 1024x768+0+0 0mm x 0mm
1024x768 0.00*
800x600 0.00
640x480 0.00
720x400 0.00
1920x1080_60.00 (0x1b9) 173.000MHz
h: width 1920 start 2048 end 2248 total 2576 skew 0 clock
67.16KHz
v: height 1080 start 1083 end 1088 total 1120 clock
59.96Hz
rhk@s31:~$ xrandr --addmode primary "1920x1080_60.00"
xrandr: Failed to get size of gamma for output default
xrandr: cannot find output "primary"
rhk@s31:~$
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