Problem with dual 4k on Hp Dock G2 and Elitebook 840 G7

[jqbFrnzs]

Hello everyone! I have a big issue with my new PC and dockstation display connection.

I wanted to use dual monitor setup (Dell U2718Q and Lenovo L28u-30 monitors) with my Elitebook 840 G7 and Dock G2 HSN-IX01 (2UK37AA ). The problem is they don't work in 4k resolution simultaneously, but only when plugged separately. Due the specification the dock station is capable of handling dual 4k monitors - 3840 x 2160 @60Hz  on 2 DP ports (or 1 DP + 1 USB-C® Alt mode port or 1 DP + 1 TB port or 1 TB + 1 USB-C® alt mode) on DP 1.3 Thunderbolt™ host. I checked the firmware, but all of it was up to date - I reflashed the firmware anyway, but without effect. The connected displays are fully functional when plugged both to dock, but one of them always won't show me the option to set 4k in Windows display option (max is 1920x1080 on Lenovo and 2048x1080 on Dell [which is weird ]). It also apears that whichever monitor is plugged into right dp port at the back of dock gets 4K natively, 4k resolution on left dp port is available only when one monitor is plugged into the dock. I use minidp to dp cable for Dell and dp to dp cable for Lenovo display accordingly. I also use 120W original power supply for this dock if this thing matters. All other ports work as expected.

What could be the source of the problem?

Can it be that dock doesn't support dual 4k over display ports, despite this feature being listed in specification?

Would display port to usb-c adapter / minidp to usb-c adapter / display port to usb-c cable  solve this issue, as this dock has port Type-C® USB 3.1 Gen 2 port with DisplayPort™ 1.4 data and power out (15W) ?

Thanks in advance for any help solving this problem.

Below, I provide relevant datasheets and specifications:

dock: https://h20195.www2.hp.com/v2/GetDocument.aspx?docname=c04168358 (search for 2UK37AA)

PC: https://www8.hp.com/h20195/v2/GetDocument.aspx?docname=4AA7-6811ENUC

Lenovo display: https://www.lenovo.com/gb/en/accessories-and-monitors/monitors/home/L28u-30C19280DL028inch-MonitorHD...

Dell display: https://www.displayspecifications.com/en/model/fed0d61

[banhien · Accepted solution]

@jqbFrnzs 

Your machine supports DP 1.4, for 2 4K monitors, please try to connect the following ways:

• 2 DP ports or
• 1 DP + 1 USB-C® Alt mode port or
• 1 DP + 1 TB port or
• 1 TB + 1 USB-C® alt mode

More information:

            https://www8.hp.com/h20195/v2/getpdf.aspx/c04168358

Regards

[jqbFrnzs]

I know the docs and specs, but it doesn't work at 4k 60Hz with dual dp ports  of the dock. Also I don't have dp to usb-c adapter or cable and don't know if it is worth investing. Everything should work out of the box, but here it is... big failure unfortunetely.

Regards

~ Jqb

[jqbFrnzs]

Can you provide any additional support for this case? On friday I would be able to check displayport to usb-c cable. For now I am stuck with current, unsatisfactory scenario.

Regards

~ Jqb

[jqbFrnzs]

Today my usb-c to dp cable arrived. 2 x 4k at 60Hz works using tb port and normal dp port. I never figured out why 2x dp doesn't work properly, but anyway... my setup is up and running properly now! Thanks for your help!