Procedure:Chymera X11 setup

Chymera X11 setup info

This page describes how to get the 8K display output from Chymera in the Streisenger 472 conference room.

Problems not yet resolved

Autostupid monitor rearrangement

I have searched far and wide but have yet to find the magical xorg.conf incantation which will tell the system "never attempt to automatically rearrange the displays, period, for any reason."

If a panel is

• Switched on
• Even begins receiving a video stream on a different HDMI port than currently in use (e.g. a laptop is connected to a different port)

, the panel will send some sort of signal via HDMI to Chymera. Even if Chymera is not currently set to use that panel (e.g. it is using the left two displays, or only one), X or Gnome (I'm not sure which) will take the signal and respond by more or less completely trashing everything about the current monitor arrangement. Every time it happens.

Strange DisplayPort problem

There is, apparently, some form of defect in DisplayPort wherein if the GPU decides the monitor went to sleep, it will never, ever output to that port again until the connection is physically unplugged and replugged. If this occurs (e.g. nvidia-settings shows everything is arranged right but one panel is blank), you really do have no recource but to physical pull the adapter from the cards (not the hdmi cable from the adaptor) and replug.

Physical layout

The monitors are known to the system in the following order:

+------+------+
| DP-5 | DP-4 |
+------+------+
| DP-6 | DP-7 |
+------+------+

On paper the following xrandr command should throw all panels on and into the correct position, resolution and orientation:

xrandr --fbmm 1440x810 \
       --output DP-4 --mode 3840x2160  --pos +3840x+0  --reflect xy \
       --output DP-5 --mode 3840x2160  --pos +0x+0     --reflect xy \
       --output DP-6 --mode 3840x2160  --pos +0x+2160  \
       --output DP-7 --mode 3840x2160  --pos +3840x+2160

In reality, unless all four screens are already on, it is slightly less reliable than a desperate meth addict and I've had it mangle the arrangement so bad that using nvidia-settings' expert mode was necessary.

The only method I know of which is more than fractionally reliable to arrange them is to manually set this up in nvidia-settings:

• Set all panels to 3840x2160
• Set DP-4 and DP-5 to "reflect XY"
• Drag them in the layout box to match the 2x2 arrangement above

Audio not working?

Chymera can play audio from the monitors via HDMI. If this is not working:

• Click the speaker icon on the launch bar
• Does it show no output hardware other than "Dummy?"

Then the problem is that you aren't in the system's "audio" group (having been authenticated by LDAP which doesn't know about per-system requirements) and are being denied access to /dev/snd (whose devices are owned by root:audio and are chmod 660).

If you do not have superuser access, you will have to ask for your user name to be added to the audio group in /etc/group on Chymera.