Fatal DPMS issues with multihead/multiseat machine

Erik Walthinsen omega at vcolo.com
Tue Aug 30 12:37:24 PDT 2005

I'm building a machine with 6 video cards and associated USB keyboards
and mice ("multiseat"), for a school in the middle Bolivia.  We're
packing the machine up this Friday (Sept 2nd) and flying there on
Sunday.  Problem is, it doesn't work properly yet.

I've finally traced the issues down to DPMS.  What it boils down to is a
case of the monitor(s) going to sleep and not waking up again.  I've
tried a number of configurations:

1) DPMS disabled completely:

In this case, the monitors themselves decide to go to sleep eventually,
and do not wake up.  The only thing I can think of is that the LCDs have
been kicked into DPMS mode by previous instances of X, so I'm currently
running a test where the LCDs have been powered off and unplugged before
booting the machine, and the int10 hack I have to do for multi-seat
operation has DPMS disabled explicitly in addition to the main X servers.

2) DPMS enabled and timeouts set to zero:

Again the monitors seem to go to sleep on their own in this case, and
never wake back up.

Interestingly, this is the one mode in which I can easily *force* the
issue.  Running `xset dpms 1 2 3` will cause the monitors to blank
within 2sec and never come back without a full reboot.  If it comes to
debugging the exact sequence of events, this is a *major* benefit as I
don't have to wait for the setup to die on its own (lengthy) schedule.

3) DPMS enabled normally:

Normal operation until X decides to shut down the monitor, at which
point it's game over.

Someone suggested switching resolutions to get the monitor to wake up,
but that does nothing at all.  Nothing I do with xset will bring the
display back.

Periodically the machine actually hangs solid when I try to recover.
Sometimes it will hang when I shut down GDM and restart it, but more
often it just doesn't ever bring the monitor back.

OK, another very odd situation.  I brought the machine up with DPMS
completely disabled, the ran the aforementioned `xset dpms 1 2 3`.
Instead of blanking and not coming back, the screen went black for a few
seconds (*normal* X "screensaver"), then came back, and repeated this
several times, without ever doing a DPMS blank.


Running Ubuntu 5.04 latest packages, including xserver-xorg-6.8.2-10.
Current kernel is 2.6.13 stock, but no changes with
linux-image-386_2.6.10-7, 2.6.11, or Backstreet Ruby patches on 2.6.11.

Because the secondary video cards are very unhappy running with
SingleCard before they've been initialized with their respective BIOSs,
I have to run X with the following xorg.conf first:


Then I can start each of the displays with the appropriate configs:


By way of the gdm.conf file as per:


I'm getting *very* desperate to get this solved, as if this doesn't work
we're suddendly stuck with a lot of relatively expensive gear that's
totally unusable, and we only end up installing *2* workstations
(redundant gear) instead of 6...

   aka Erik Walthinsen
   omega at vcolo.com

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