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I have Lenovo ThinkPad t470p with docking station Lenovo ThinkPad Ultra Dock 170W 40A20170EU. This docking station has 2x DisplayPort 1.2. I connected two 4k monitors (LG 27UK850-W) via DisplayPorts.

Ubuntu 18.10 recognizes both monitors, but doesn't allow to enable two 4k monitors with 3840x2160 resolution (but it allows one monitor in 3840x2160 and one in 1600x900).

However on Windows 10 it works, so I believe it is a software limitation. Can you please tell what should I do to provide more information or solve an issue?

edit: deleted information about "hardware limitations", it was because two displays had different scale (100% and 200%).

xrandr output:

Screen 0: minimum 320 x 200, current 6400 x 2160, maximum 8192 x 8192
eDP-1 connected primary 2560x1440+0+0 (normal left inverted right x axis y axis) 309mm x 174mm
   2560x1440     60.05*+  59.99    59.99    59.96    59.95  
   1920x1440     60.00  
   1856x1392     60.01  
   1792x1344     60.01  
   2048x1152     59.99    59.98    59.90    59.91  
   1920x1200     59.88    59.95  
   1920x1080     60.01    59.97    59.96    59.93  
   1600x1200     60.00  
   1680x1050     59.95    59.88  
   1600x1024     60.17  
   1400x1050     59.98  
   1600x900      59.99    59.94    59.95    59.82  
   1280x1024     60.02  
   1440x900      59.89  
   1400x900      59.96    59.88  
   1280x960      60.00  
   1440x810      60.00    59.97  
   1368x768      59.88    59.85  
   1360x768      59.80    59.96  
   1280x800      59.99    59.97    59.81    59.91  
   1152x864      60.00  
   1280x720      60.00    59.99    59.86    59.74  
   1024x768      60.04    60.00  
   960x720       60.00  
   928x696       60.05  
   896x672       60.01  
   1024x576      59.95    59.96    59.90    59.82  
   960x600       59.93    60.00  
   960x540       59.96    59.99    59.63    59.82  
   800x600       60.00    60.32    56.25  
   840x525       60.01    59.88  
   864x486       59.92    59.57  
   800x512       60.17  
   700x525       59.98  
   800x450       59.95    59.82  
   640x512       60.02  
   720x450       59.89  
   700x450       59.96    59.88  
   640x480       60.00    59.94  
   720x405       59.51    58.99  
   684x384       59.88    59.85  
   680x384       59.80    59.96  
   640x400       59.88    59.98  
   576x432       60.06  
   640x360       59.86    59.83    59.84    59.32  
   512x384       60.00  
   512x288       60.00    59.92  
   480x270       59.63    59.82  
   400x300       60.32    56.34  
   432x243       59.92    59.57  
   320x240       60.05  
   360x202       59.51    59.13  
   320x180       59.84    59.32  
DP-1 disconnected (normal left inverted right x axis y axis)
HDMI-1 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected (normal left inverted right x axis y axis)
HDMI-2 disconnected (normal left inverted right x axis y axis)
DP-3 disconnected (normal left inverted right x axis y axis)
HDMI-3 disconnected (normal left inverted right x axis y axis)
DP-3-1 connected 3840x2160+2560+0 (normal left inverted right x axis y axis) 600mm x 340mm
   3840x2160     60.00*+  30.00  
   2560x1440     59.95  
   1920x1080     60.00    60.00    59.94  
   1600x900      60.00  
   1280x1024     60.02  
   1280x800      59.81  
   1152x864      59.97  
   1280x720      60.00    60.00    59.94  
   1024x768      60.00  
   800x600       60.32  
   720x480       60.00    59.94  
   640x480       60.00    59.94    59.94  
DP-3-2 connected (normal left inverted right x axis y axis)
   3840x2160     60.00 +  30.00  
   2560x1440     59.95  
   1920x1080     60.00    60.00    59.94  
   1600x900      60.00  
   1280x1024     60.02  
   1280x800      59.81  
   1152x864      59.97  
   1280x720      60.00    60.00    59.94  
   1024x768      60.00  
   800x600       60.32  
   720x480       60.00    59.94  
   640x480       60.00    59.94    59.94  
DP-3-3 disconnected (normal left inverted right x axis y axis)

driver info: (output lshw -c video)

  *-display                 
       description: 3D controller
       product: GM108M [GeForce 940MX]
       vendor: NVIDIA Corporation
       physical id: 0
       bus info: pci@0000:02:00.0
       version: a2
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress bus_master cap_list
       configuration: driver=nvidia latency=0
       resources: irq:142 memory:f3000000-f3ffffff memory:e0000000-efffffff memory:f0000000-f1ffffff ioport:d000(size=128)
  *-display
       description: VGA compatible controller
       product: Intel Corporation
       vendor: Intel Corporation
       physical id: 2
       bus info: pci@0000:00:02.0
       version: 04
       width: 64 bits
       clock: 33MHz
       capabilities: pciexpress msi pm vga_controller bus_master cap_list rom
       configuration: driver=i915 latency=0
       resources: irq:140 memory:f2000000-f2ffffff memory:c0000000-dfffffff ioport:e000(size=64) memory:c0000-dffff

CPU info: (output of cat /proc/cpuinfo)

processor   : 0
vendor_id   : GenuineIntel
cpu family  : 6
model       : 158
model name  : Intel(R) Core(TM) i7-7700HQ CPU @ 2.80GHz
stepping    : 9
microcode   : 0x8e
cpu MHz     : 1763.195
cache size  : 6144 KB
physical id : 0
siblings    : 8
core id     : 0
cpu cores   : 4
apicid      : 0
initial apicid  : 0
fpu     : yes
fpu_exception   : yes
cpuid level : 22
wp      : yes
flags       : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc art arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf tsc_known_freq pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault epb invpcid_single pti ssbd ibrs ibpb stibp tpr_shadow vnmi flexpriority ept vpid fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms invpcid mpx rdseed adx smap clflushopt intel_pt xsaveopt xsavec xgetbv1 xsaves dtherm ida arat pln pts hwp hwp_notify hwp_act_window hwp_epp flush_l1d
bugs        : cpu_meltdown spectre_v1 spectre_v2 spec_store_bypass l1tf
bogomips    : 5616.00
clflush size    : 64
cache_alignment : 64
address sizes   : 39 bits physical, 48 bits virtual
power management:
(7 other cores skipped for brevity)

Yes I installed additional driver from official Nvidia website for my graphic card (940MX and Linux 64bit)

  • xrandr reports a maximum overall resolution of 8192 x 8192. The widths of your internal display and one 4k monitor add up to 6400 pixels, which means there are only 1792 pixels left for the other monitor. If it worked in windows 10, it's probably a driver issue. Did you install any additonal drivers? The exact specs of your computer are also important: which CPU, which GPU? – danzel Jan 11 at 12:59
  • @danzel added additional information about CPU, GPU and drivers – addmeaning Jan 15 at 18:58

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