Compatibility with dell docks

@Terryparker  The TB16 and the D3100 operate in vastly different ways. Any information you can provide about the actual displays you’re working with and exactly how you’re trying to connect them (which output on the dock to which input on each display) would likely be helpful.

Hi JP

One monitor is Dell U2515H

The other is Kogan 34" WQHD 21:9 Ultrawide 75Hz Monitor (3440 x 1440)

Both work separately via hdmi and display port.

I can switch monitor via unplugging one and it'll detecting the other. If i plug the first back in it will generally not display, sometimes it will switch back to the first monitor, though i can sometimes hit the powerbutton on the dock and it will then switch.

At no time can i have 2 external monitors attached via the display.

I have swapped both monitors from hdmi to dp and back but no combination works. I've bought new cables from OW also.

I never have used power to laptop via the dock.

Dell support have no answer other than now saying the dock isn't on the compatibility list.

@Terryparker  Dell doesn't list any Inspiron systems on their dock compatibility list because they don't implement the necessary firmware-level support for certain dock features into their Inspiron systems, such as support for being controlled by the dock's Power button, PXE boot, and MAC Address Passthrough.  But that doesn't mean that the core functionality of the docks won't work.  In fact the Dxxxx series docks are specifically billed as "universal".  I've even used Dell docks with Lenovo systems and vice versa, and those proprietary features don't work in a mixed configuration like that, but otherwise they work fine.

That said, the D3100 won't support that pair of displays.  It's just more than the chipset in that dock can handle.  If you want the standard 60 Hz refresh rate, the most you can achieve with dual displays is 1080p each.  That's laid out in the D3100's user guide.  But Dxxxx docks should be avoided anyway whenever your system allows a better configuration anyway because Dxxxx docks use "indirect display" technology called DisplayLink -- not to be confused with DisplayPort -- and that comes with some drawbacks that can be significant and that I wrote about here.

As for the TB16, you should be able to achieve up to dual 4K 60 Hz with that dock, so what you're describing there is unexpected.  Are you current on your system BIOS, system Thunderbolt controller firmware, and TB16 firmware?  If so, have you tried using the DP + mini-DP, or perhaps using a USB-C to DP cable/adapter to use the downstream/peripheral TB3 port as a display output?  DP+HDMI should work, but if it doesn't, then you might find that you can still work around it using other combinations.  If you don't have the appropriate cables for that, they're not especially expensive or hard to find, and they'd be easy to return if they don't solve your issue.

Hi

Everything is uptodate.

All cables work in various combinations - just can't get both working together.

As a side note, the NVidia Control Panel can only detect one monitor - any chance this is the issue Note - I'm running the latest firmware and it cannot detect when option "My display is not showing")

Nvidia will pickup either monitor (when only 1 attached separately)

I have swapped cables to both external monitors - same result.