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Multi Monitor Requirements
The U442-DOCK4-S supports the connection of two monitors at the same time through
DisplayPort Multi-Stream Transport (MST) mode. As DisplayPort MST mode is being used,
this requires the DisplayPort to be one of the two video ports being used at the same
time. Connect either a DisplayPort monitor and HDMI monitor at the same time or a
DisplayPort monitor and VGA monitor. Do not connect an HDMI and VGA monitor. Below
are limitations that must be taken into account when connecting multiple monitors at the
same time.
Does the Source Computer Support DisplayPort MST Mode?
When connecting to a USB-C source that supports DisplayPort MST mode, the EDID
information of both connected monitors will be read by the computer and appear as
separate displays that can be shown in mirror mode or extended mode. When connected
in MST mode, the computer graphics card will first allocate bandwidth for the DisplayPort
monitor, with the remaining bandwidth going to the non-DisplayPort monitor. If the
DisplayPort monitor supports a maximum 4K resolution at 30 Hz, bandwidth will be
allocated to allow it to be displayed in 4K at 30 Hz. The non-DisplayPort monitor will be
limited to the remaining bandwidth left by the graphics card, meaning it may be forced
to display in 1920 x 1080 or lower resolutions, even if it has the capability of displaying
higher resolutions.
Note:
Even if the DisplayPort monitor’s resolution is lowered, the same amount of bandwidth will be
allocated for it by the computer. In other words, you will not be able to obtain a higher resolution on
the non-DisplayPort monitor by lowering the resolution on the DisplayPort monitor.
When connecting to a USB-C source that does not support DisplayPort MST mode,
Single-Stream Transport (SST) mode is used instead. In SST mode, only the EDID of
the first connected monitor is read by the computer, forcing the connected monitors to
display in mirror mode. The default resolution of the first monitor will then be sent to the
second monitor, with both monitors displaying the same resolution. If the second monitor
is not capable of supporting the same resolution as the first, no video will display on that
monitor. Before connecting the second monitor, the first monitor’s resolution must be
changed to the second monitor’s resolution in order for video to be displayed.
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