[mdlug] dual monitor configuration has snow for particular app [Was: [mdlug-newbie] dual monitor configuration has snow for particular app ]

Dr. Robert Meier list1c30fe42 at bellsouth.net
Wed May 10 15:48:30 EDT 2017


MDLUGers,

I am cross-posting (shame on me) this message because it has gotten
zero response on the mdlug-newbie list.

I hope that we will see Rich this weekend 2017.05.12,
but it would help if someone can help him with this issue beforehand.
If this problem cannot be resolved by email before Saturday,
perhaps narrowing down hardware suspects can make it practical to
bring the hardware this Saturday to demo a working arrangement
or perform hardware diagnosis.

-------- Forwarded Message --------
Subject: 	Re: [mdlug-newbie] dual monitor configuration has snow for
particular app
Date: 	Sat, 22 Apr 2017 19:47:00 GMT
From: 	musichall at juno.com <musichall at juno.com>
Reply-To: 	A place where there are no dumb (linux related) questions.
<mdlug-newbie at mdlug.org>
To: 	mdlug-newbie at mdlug.org



Hello,
Thanks for your quick response... can't say the same for me!
This is pertaining to the GUI operation. And it's not just pertaining to
some app, it's the whole OS -- with nothing running (no application
selected). I get the snow straight out of the gate (so to speak): boot
-> snow on both monitors.
As for the snow -- Not sure from your comment if you knew what I meant
by snow. It is essentially the same as tuning an analog TV to a channel
where there is no broadcast signal: 'snow'. In the audio domain, tuning
a radio to an AM station to a frequency where there is no broadcast
signal: just noise. And in the process of illustrating that, I thought
it might be appropriate to see if the is the same with both video and
audio. I had some audio file playing, then connected the other monitor,
waited for the screen to Go-Snow, to see if the audio was affected.
Audio was not affected.
As for an electrical problem: I would have to say NO. It works with
every other OS I've used on this machine, including the present instance
of Windows XP (x64). It just works!! But I appreciate your thoroughness
--  covering the bases.
Nevertheless when I booted to Mint again, all I got was the command-line
log-in, which threw me (not used to that with the latest distros of
Linux). It took several minutes before I realized that the login text
WAS the login for the OS, not just some error message. So, the GUI is
gone now -- I don't know what happened -- I DIDN'T TOUCH ANYTHING -- it
just changed (which is confusing because it's code: it's deterministic
!!) So I booted to the Live disc, to see what I could see for answering
your questions.  The following is the output of the command you gave me
(using the Live disc. I presume the setting would be close, if not the
same, because I get the same result with both monitors with the Live disc):
mint at mint ~ $ ps -ef|grep X
root 1806 1801 1 18:56 tty7 00:00:07 /usr/lib/xorg/Xorg :0 -audit 0
-auth /var/lib/mdm/:0.Xauth -nolisten tcp vt7
mint 2847 2793 0 19:03 pts/0 00:00:00 grep --color=auto X
mint at mint ~ $
As for the apps that cause the screen-saver to freeze (lock-out): again,
with the Live disc (since the GUI of the installed instance of it is
gone), so far I was able to see that Firefox caused it to lock-out.
However, when I booted to the Live disc, When I booted the Live disc, I
forgot about the two monitors connected, went to get something to drink
(while the OS booted from the DVD), came back, and the screen-saver had
engaged. I pressed some keys: nothing; moved the mouse: nothing. I
figured I needed to reboot so I pressed Ctl-Alt-Del (force of habit with
Windows), and somewhere in that process caused the [GUI] screen to
return. Perhaps I was using the wrong method to recover from the
screen-saver? On the other distros that I have (Ubuntu, Centos, SLAMPP -
all that I've used so far, anyway), any action: keyboard or mouse,
recovers from the screen-saver. Still not sure yet of the boundaries of
it all.
Any help or insight is greatly appreciated.
Rich Hall

---------- Original Message ----------
From: "Dr. Robert Meier" <list1c30fe42 at bellsouth.net>
To: mdlug-newbie at mdlug.org
Subject: [mdlug-newbie] dual monitor configuration has snow for
particular app
Date: Sun, 16 Apr 2017 22:26:29 -0400

[The following is a relay to this list.
   The original questioner had difficulty posting,
     but should now be able to read and reply to this list.]

Xperts,

  > ..., I have a dual-monitor video card
  > (specifically one VGA and one DVI output).
  > The brand is ATI (which is now AMD, model 9600 Pro
  > using the RV350 chip/chipset), ...
  > [the] behaviour is pretty much as expected.
  > But if I plug in the second monitor,
  > the other monitor lights up and
  > the screen on BOTH monitors results in white snow
  > - no actual discernible image.
  > If I disconnect it fairly soon afterward,
  > the remaining screen returns to the 'normal' state.
  > If I don't disconnect it soon,
  > the machine (actually the video) is hosed,
  > and I must use the 1/0 button to get back to an active screen

I've never seen or heard of 'white snow'
   (?random intensity distribution?)
   resulting from digital misconfiguration.

Is it possible that you suffer a ground loop[1]
   (common hardware problem)?
Are both monitors' shields (i.e. nominally screws
   on the video connector) screwed in? [yes]
Are your wall power sockets grounded? [yes]
Are you using a polarized outlet adapter[2]? [no]

Please post your X configuration.
Depending on your X implementation (Xorg, XFree86, ???)
    the config file(s) might be one or more of
      /etc/Xorg.conf
      /etc/xorg.conf
      /etc/X11/xorg.conf
      /etc/X11/xorg.conf.d/*
      /etc/XFree86Config
      /etc/X86Config
      ...
If you don't know your X implementation,
    please post the output of
      ps -ef | grep X
which should include your X implementation
    and is likely to name your X configuration file(s).

  > Secondly, as for the screen saver:
  > If I do NOT have an application open and the screen saver kicks in,
  > the active screen can be recovered (as you would expect).
  > But if I DO have an application open and the screen saver kicks in,
  > I must use the 1/0 button to return to using the computer.

Please post the identity of at least TWO applications
   that exhibit this behavior.
Do you have another laptop, cellphone, or computer? [yes]
Can you use ssh to remotely log into the problem computer computer
   from the second computer?
Using the remote login twice to run
      ps -ef
   can you post the results with an application open
    before the screen saver kicks in
    AND after the screen saver kicks in

  > From my perspective,
  > the first problem appears to be a VERY poorly written video driver
  > or interface with the OS.
  > The hardware is old enough to have decent drivers available,
  > but not so old as to not have any reasonable drivers available
  > ANY MORE.
  > The second problem appears to be
  > some sort of instability within the OS itself:
  > (Why would an open app make any difference for the screen saver ?)
  > It's all very frustrating for me
  > because I expected more stability and predictability from Linux,
  > whatever the specific flavor
  > (e.g. Red Hat/Centos, Ubuntu, Debian/Mint, etc).

Relaying,
--
Bob

[1] See https://en.wikipedia.org/
        wiki/Ground_loop_%28electricity%29
      section Ground loops in digital and RF systems
        for an explanation and
[2] Polarized outlet adapter
      http://www.acehardware.com/product/index.jsp
        ?productId=1285936
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