From Newsgroup: comp.os.linux.misc


I've been trying to set my 3 1920x1080 monitors up to look like a 1920-
plus a 3840-wide screen.

The recipe seems to be something like:

xrandr --setmonitor xyzzy 3840/1086x1080/302+1920+0 HDMI-0,HDMI-1-2

xrandr --fb 5761; xrandr --fb 5760 # see https://chipsenkbeil.com/notes/linux-virtual-monitors-with-xrandr/

and this seems successful:

xrandr --listmonitors
Monitors: 2
0: xyzzy 3840/1086x1080/302+1920+0 HDMI-0 HDMI-1-2
1: +DP-1 1920/543x1080/302+0+0 DP-1


However, when I run either of LO Impress or OBS Studio, neither
recognizes the extended monitor. Each lists two monitors (rather than
three), but treats both as 1920 wide. So my presentation display is
scaled down. Not what I need.

Can anyone advise how to do this please?

Thanks.
--
Mike Scott
Harlow, England

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From Newsgroup: comp.os.linux.misc

On 12/20/25 04:23, Mike Scott wrote:

I've been trying to set my 3 1920x1080 monitors up to look like a 1920-
plus a 3840-wide screen.

The recipe seems to be something like:

xrandr --setmonitor xyzzy 3840/1086x1080/302+1920+0 HDMI-0,HDMI-1-2

xrandr --fb 5761; xrandr --fb 5760      # see https://chipsenkbeil.com/ notes/linux-virtual-monitors-with-xrandr/

and this seems successful:

xrandr --listmonitors
Monitors: 2
 0: xyzzy 3840/1086x1080/302+1920+0  HDMI-0 HDMI-1-2
 1: +DP-1 1920/543x1080/302+0+0  DP-1

However, when I run either of LO Impress or OBS Studio, neither
recognizes the extended monitor. Each lists two monitors (rather than three), but treats both as 1920 wide. So my presentation display is
scaled down. Not what I need.

Can anyone advise how to do this please?

Um ... seems you're trying to defeat reality.

MIGHT be faked, on a limited scale, but you're
clearly running OFF that scale already. Few
apps will recognize your weird tweaks.

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From Newsgroup: comp.os.linux.misc

On Sat, 12/20/2025 4:23 AM, Mike Scott wrote:

I've been trying to set my 3 1920x1080 monitors up to look like a 1920- plus a 3840-wide screen.

The recipe seems to be something like:

xrandr --setmonitor xyzzy 3840/1086x1080/302+1920+0 HDMI-0,HDMI-1-2

xrandr --fb 5761; xrandr --fb 5760      # see https://chipsenkbeil.com/notes/linux-virtual-monitors-with-xrandr/

and this seems successful:

xrandr --listmonitors
Monitors: 2
 0: xyzzy 3840/1086x1080/302+1920+0  HDMI-0 HDMI-1-2
 1: +DP-1 1920/543x1080/302+0+0  DP-1

However, when I run either of LO Impress or OBS Studio, neither recognizes the extended monitor. Each lists two monitors (rather than three), but treats both as 1920 wide. So my presentation display is scaled down. Not what I need.

Can anyone advise how to do this please?

Thanks.

First I'd give you a little hardware background.

This is AMD Eyefinity, as rolled out on a custom gamer desk AMD used for a P.R. win.
(Apparently the NVidia equivalent is called NVidia Surround.)

+-----------+-----------+-----------+
| 1920x1080 | 1920x1080 | 1920x1080 | ---- head0 --- Crossbar counter uses 5760x1080
+-----------+-----------+-----------+
+-----------+-----------+-----------+
| 1920x1080 | 1920x1080 | 1920x1080 | ---- head1 --- Crossbar counter uses 5760x1080
+-----------+-----------+-----------+

This appears as two monitors where the crossbar claims a virtual monitor
exists which is 5760 pixels wide. One reason this works, is the three
monitors across are identical, and that makes configuring the thing at
hardware level, a lot easier to do. The crossbar count is hinted to be
up to 16384 counts, so you might run three identical 5K monitors as a virtual panoramic monitor.

The second row of monitors could be a different set of dimensions
(three 2560x1600 if you wanted), but then the gamer desk would look
a little silly if done that way. It looks better if the 2D matrix of monitors is all done with the same model of monitor (thin bezels).

The crossbar could be programmed for fewer monitors, such as
combining your two monitors. You could do a 2x2 monitor set, as
two virtual monitors. And the crossbar counter is 3840 wide if using
the same monitors as in the picture.

With that little intro behind us, then the question is

"Does the desktop have the ability to properly manage Eyefinity mode ?"

I don't know the answer to that. The thread here, hints that it is (unnecessarily) complicated.

https://bbs.archlinux.org/viewtopic.php?id=264701

# Surround and Eyefinity aren't in here...

https://wiki.archlinux.org/title/Xrandr

# Example of shenanigans, before Window Managers starts and after X starts

~/.xinitrc
...
{ sleep 2; xrandr xrandr_parameters } &

The question then would be, does the Xserver need to be concatenated before
the Windows Manager starts ? Or can displays be concatenated after the
Windows Manager is running ?

Matrox (a graphics card company in Canada), made adapter boxes.
One supports one monitor signal in, driving two surround monitors.
The other product could drive three monitors. The three monitor
one would claim to the OS to be a "5760x1080" monitor, and then
the video card was not doing any fancy crossbar shit. The external
box did it.

TripleHeadToGo

https://video.matrox.com/en/products/gxm/triplehead2go-series/dp-edition

(discontinued, replace by QuadHeadToGo)

https://video.matrox.com/en/media/1616/download

QuadHeadToGo (looks commercial rather than consumer-oriented, follow the money)

https://video.matrox.com/en/products/video-walls/quadhead2go-series

That would be one way to fool a computer into doing the right thing.

Paul
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From Newsgroup: comp.os.linux.misc

On Sat, 12/20/2025 6:14 AM, Paul wrote:

On Sat, 12/20/2025 4:23 AM, Mike Scott wrote:

I've been trying to set my 3 1920x1080 monitors up to look like a 1920- plus a 3840-wide screen.

The recipe seems to be something like:

xrandr --setmonitor xyzzy 3840/1086x1080/302+1920+0 HDMI-0,HDMI-1-2

xrandr --fb 5761; xrandr --fb 5760      # see https://chipsenkbeil.com/notes/linux-virtual-monitors-with-xrandr/

and this seems successful:

xrandr --listmonitors
Monitors: 2
 0: xyzzy 3840/1086x1080/302+1920+0  HDMI-0 HDMI-1-2
 1: +DP-1 1920/543x1080/302+0+0  DP-1


However, when I run either of LO Impress or OBS Studio, neither recognizes the extended monitor. Each lists two monitors (rather than three), but treats both as 1920 wide. So my presentation display is scaled down. Not what I need.

Can anyone advise how to do this please?

Thanks.

First I'd give you a little hardware background.

This is AMD Eyefinity, as rolled out on a custom gamer desk AMD used for a P.R. win.
(Apparently the NVidia equivalent is called NVidia Surround.)

+-----------+-----------+-----------+
| 1920x1080 | 1920x1080 | 1920x1080 | ---- head0 --- Crossbar counter uses 5760x1080
+-----------+-----------+-----------+
+-----------+-----------+-----------+
| 1920x1080 | 1920x1080 | 1920x1080 | ---- head1 --- Crossbar counter uses 5760x1080
+-----------+-----------+-----------+

This appears as two monitors where the crossbar claims a virtual monitor exists which is 5760 pixels wide. One reason this works, is the three monitors across are identical, and that makes configuring the thing at hardware level, a lot easier to do. The crossbar count is hinted to be
up to 16384 counts, so you might run three identical 5K monitors as a virtual panoramic monitor.

The second row of monitors could be a different set of dimensions
(three 2560x1600 if you wanted), but then the gamer desk would look
a little silly if done that way. It looks better if the 2D matrix of monitors is all done with the same model of monitor (thin bezels).

The crossbar could be programmed for fewer monitors, such as
combining your two monitors. You could do a 2x2 monitor set, as
two virtual monitors. And the crossbar counter is 3840 wide if using
the same monitors as in the picture.

With that little intro behind us, then the question is

"Does the desktop have the ability to properly manage Eyefinity mode ?"

I don't know the answer to that. The thread here, hints that it is (unnecessarily) complicated.

https://bbs.archlinux.org/viewtopic.php?id=264701

# Surround and Eyefinity aren't in here...

https://wiki.archlinux.org/title/Xrandr

# Example of shenanigans, before Window Managers starts and after X starts

~/.xinitrc
...
{ sleep 2; xrandr xrandr_parameters } &

The question then would be, does the Xserver need to be concatenated before the Windows Manager starts ? Or can displays be concatenated after the Windows Manager is running ?

Matrox (a graphics card company in Canada), made adapter boxes.
One supports one monitor signal in, driving two surround monitors.
The other product could drive three monitors. The three monitor
one would claim to the OS to be a "5760x1080" monitor, and then
the video card was not doing any fancy crossbar shit. The external
box did it.

TripleHeadToGo

https://video.matrox.com/en/products/gxm/triplehead2go-series/dp-edition

(discontinued, replace by QuadHeadToGo)

https://video.matrox.com/en/media/1616/download

QuadHeadToGo (looks commercial rather than consumer-oriented, follow the money)

https://video.matrox.com/en/products/video-walls/quadhead2go-series

That would be one way to fool a computer into doing the right thing.

Paul

Another hint that something isn't right with regard to monitor handling (using the hardware feature Eyefinity/Surround to achieve a result).

https://www.reddit.com/r/linux_gaming/comments/1pdoafv/amd_eyefinity_on_fedora_linux_triple_portrait/

Xrandr should not be attempting to "fuse" the monitors together, unless
the entire platform has the virtualization mechanism to "fake" the characteristics of the monitor when things like games ask for the details.

If the monitors are handled individually, the results would be "more conventional".

Paul

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