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I own a pretty old Samsung BX2250 monitor, which I would like to be able to set to standby using dpms, like

xset dpms force off

The expected result is the monitor going to standby. The actual result is, that the monitor turns black, then it says "Check Signal Cable".

I also messed around with

xset s off

as I read somewhere this interferes with dpms, with the result that the screen turns back on immediately. Using standby and suspend does not help either.

I own a GeForce GTX 960 graphics card, using the nvidia-440xx driver on a Manjaro, which uses x11 (by trying this: How to know whether Wayland or X11 is being used).

I remember back some days with my old PC, it went to standby mode. Unfortunately, I cannot remember what I did to achieve that. Does anyone have suggestions?

2 Answers 2

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The answer to the question above was to use a HDMI cable supporting DPMS signals.

Note (to avoid the pitfall I fell for): The outer diameter of the cable does not indicate nothing about this. I tried 6 cables in total, the last one did the trick.

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DPMS in X11 has three phases (apart from on) which are standby, suspend, and off. You might want to try running

xset dpms force standby

or

xset dpms force suspend

But be aware that it is not always possible to do all of these operations. You can check the Xorg log (might be somewhere in /var/log/Xorg.0.log for the current session, the 0 in there is a screen number and it might be different too) and see what DPMS features are actually supported. On my system when I check for that:

$ grep DPMS /var/log/Xorg.0.log
[    31.954] (II) AMDGPU(0): DPMS capabilities: Off
[    31.970] (==) AMDGPU(0): DPMS enabled
[    31.989] (II) Initializing extension DPMS

I can see that the only state my GPU driver supports is off. That does not mean suspend and standby won't work, but rather that it will actually use the off action instead, even when I do xset dpms force suspend for example.

If, however, you just want the screen to be black, but be usable really fast after a key press or mouse event, then what you might want to look into is simple screen-saver. You must turn off "Quick Power-off in Blank Only Mode" for xscreensaver if you are using that, otherwise it will again just power off your monitor instead.

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  • I checked my Xorg log and it said: $ grep DPMS /var/log/Xorg.0.log [ 13.568] (**) NVIDIA(0): DPMS enabled [ 13.572] (II) Initializing extension DPMS Compared to your output, my log is missing out on the DPMS capabilities line. Does that mean that the device/driver is not capable of any DPMS action?
    – MP Felder
    Commented Jun 11, 2020 at 21:44
  • @MPFelder Not necessarily, it might just be different log level that's used for that or the driver does not report it. You definitely have some capabilities there. What does xset dpms force standby do?
    – nert
    Commented Jun 11, 2020 at 22:03
  • Nothing extraordinary. The screen turns black and the monitor displays the "Check Signal Cable"...
    – MP Felder
    Commented Jun 19, 2020 at 9:38
  • @MPFelder That is exactly what happens to me when the graphics card (or possibly display) does not support any other DPMS mode than off, same as I wrote in the answer. I think there is no other option for us other than screensaver blanking (just showing black screen, but still turned on) and off, which is not what you wanted. Sorry.
    – nert
    Commented Jun 19, 2020 at 9:44
  • Thanks again @nert for your efforts. Please see my accepted answer for the disappointing solution.
    – MP Felder
    Commented Jul 22, 2020 at 22:47

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