Dell D3100 - no 4K resolution available

[gdevans]

I have the following equipment:
Dell Inspiron 17 laptop - Windows 10
Dell D3100 dock
CableCreation DisplayPort to HDMI adaptor (supports 4K at 30Hz)
QED Performance eFlex HDMI cable (supports 4K)
Sony KD-55X8005C 55" 4K TV

I installed the latest driver on my laptop, and connected the equipment. Everything appears to be working correctly. I get a good display on the TV.

However, the maximum resolution is 2048x1152. This resolution is not compatible with my display, but 1920x1080 works correctly.

I wish to run it as a UHD display at 3840x2160. I checked the Adaptor settings, then "List all modes". This does not display the 3840x2160 resolution either.

Please note that I am connected via the DisplayPort socket. I am using a DP to HDMI adaptor which is 4K compatible. I am not connected to an HDMI socket.

Does anybody have any suggestions please?

[aftersow]

Same deal. I Have a Inspiron 15 with a comsol 4K DP adapter.

4K res is no issue when running direct from the laptop, but add the dock and it is down to 2048x1152.

This is my first stop on a Google search. Will post if I find anything else.

[gdevans]

Anybody got any suggestions?

I have tested the TV and HDMI cable with a different PC. Both function fine in 4K.

This means it is either the Dock or the DisplayPort to HDMI adaptor.

[AlbanRampon]

Hello,

I missed your message the first round when I was away.

The resolution offered is the maximum of HDMI.
I believe the DP->HDMI adapter you are using is a passive adapter. Therefore it uses the DP++ feature which is, in simple terms, HDMI signals over the DP plug.
https://en.wikipedia.org/wiki/DisplayPort#Dual-mode

I suggest you get an active DP -> HDMI adapter so what is going through is actually DisplayPort and not HDMI.

Kind regards,
Alban