XPS 17 9700 + WD19TB + dual ext 4k60 Displays

Thanks so much @jphughan - that solved my problem! :-))

Now I have the internal and both external displays running at 4k 60 Hz and the fan is barely noticeable. Awesome.

I would not have imagined that it's so difficult to attach two displays correctly to that dock.

BTW, I always run my displays at native resolution and so would have swapped the display with a native full HD one in that case.

Thanks again!

@ugcm  Glad it worked.  Yeah, the WD19TB allocates its display bandwidth differently based on the type of bandwidth signal it receives.  This is spelled out in the WD19TB User Guide available on support.dell.com, and if you're curious about the gory details, I wrote up this post to explain what I believe accounts for these restrictions and why they're different between HBR2 and HBR3.

As for native resolution, you should certainly always run displays at their native resolution.  My point was merely that if you were going to stick with a 27" physical size, you shouldn't drop all the way to Full HD (1920x1080), because QHD (2560x1440) is a much better experience on a 27" display, and dual QHD displays would certainly have been possible to run as well.

@jphughan How do I switch my primary GPU?

I currently have my 9700 display off, and two 4k displays at 30fps attached to the two DP ports on the TB19 and one more 4k display at 30fps attached via USB-C directly to the laptop. Windows won't let me switch any of the displays to 60fps. Previously, when I had all three external displays attached directly to the TB19, one of them wouldn't allow 4K. Based on your answer below, I'm thinking that I might be able to attach all three displays to the TB19 and/or get 60fps on at least one display (like I used to with a TB16), if I use the discrete card instead of the Intel GPU.

Thank you.

@anotherSteve  I'll answer your question, but I don't think it's going to solve your problem, or at least it wouldn't be the ideal solution.  To switch your primary GPU, you need to have an XPS 17 9700 with an NVIDIA RTX GPU -- not the GTX GPU -- and there's a BIOS option called something like "Discrete GPU Direct Control".  I can't remember the exact wording.  But that's going to impose a heat, noise, and battery life penalty.  The reason you're not getting dual 4K 60 Hz on the WD19TB at the moment isn't because of the GPU that controls your USB-C/TB3 outputs.  It's because you're not connecting the displays appropriately in order to achieve that setup.  When the Intel GPU is primary, the XPS 17 9700 is a DisplayPort 1.2/HBR2 system.  As stated in the Display Resolution Table of the WD19TB's user guide available on support.dell.com, when using a Thunderbolt-capable DP 1.2 system, if you want dual 4K 60 Hz, one of the displays has to be connected to the "downstream" TB3 port at the edge of the dock -- NOT the USB-C output near the HDMI output.  You'd use a USB-C to DisplayPort cable/adapter to achieve that.  This has to do with how the dock allocates video bandwidth it receives from the attached system, which varies based on the DisplayPort revision the system runs.  Right now with both displays connected to the DP outputs, your two displays together are sharing only half of the total video bandwidth being sent by the system (hence dual 4K 30 Hz or a single 4K 60 Hz), while the other half is sitting unused on that downstream TB3 port.

Switching the primary GPU would actually allow you to run dual 4K 60 Hz with your current cabling setup since giving the RTX GPU direct control turns the XPS 17 9700 into a DP 1.4/HBR3 system, and when paired with that type of system, the WD19TB allocates bandwidth such that dual 4K 60 Hz with both displays connected via the DP outputs is possible.  But again, there are heat, noise, and battery life concerns with that setup, because that causes the RTX GPU to drive your built-in display as well, which means the RTX GPU will never power off.

In terms of whether you can attach a third 4K 60 Hz display directly to the system, it would depend on how many GPU interfaces are wired from the GPU to the TB3 controllers in the system, and I don't have a way to know that.  But if you find that you can't get dual 4K 60 Hz on the dock, try seeing what happens when you disconnect that third display.  If you can get dual 4K 60 Hz on the dock that way but not when attaching a third display, then you can try seeing whether it makes a difference whether that third display is connected to a TB3 port on the same side of the system as the dock or the opposite side, in case the ports on different sides are run by different TB3 controllers, but if you can't make it work at all, then it's probably not possible.

@jphughan   Thank you for the answer.  Based on your previous answer, I already moved my 3rd screen to the "downstream" USB-C port.  I now have 2x into DisplayPort and 1x into the "downstream" USB-C.  They are each running 4K at 30fps with no option to change any of them to 60fps.  With my older TB16, I was able to have all three into the dock with 1 at 60fps and the other 2 at 30fps.

I'm going to try following your instruction to change to the RTX2060 and see if that lets me get 60fps out of this.

Thank you again for the answer and for taking the time to give such a clear explanation. 

@anotherSteve  Happy to help.  The initial finding with the WD19TB was unexpected.  I would have thought that the display attached to the downstream TB3 port at the edge of the dock would have allowed 4K 60 Hz, although if you had two other displays connected to the "core" outputs of the dock, then it would be expected that they would both be limited to 4K 30 Hz since they would be sharing a single DP 1.2 interface from the system.

I'm not sure how I feel about HDR either.  My laptop's internal display has it, but I keep it disabled.  HDR support in Windows is still a mess because so few applications are optimized for it.  It's great in a TV/streaming box type of setup where you're only ever viewing one thing at a time and thus switching between HDR and SDR based on what you're viewing is perfectly feasible.  But if you're trying to watch an HDR video in a window on a display that is also showing a bunch of other SDR content, then in order to get your HDR content looking right, your SDR content won't look right.  Windows relatively recently introduced the slider in the HDR settings to adjust how SDR content is presented when the display is in HDR mode, which helped quite a bit, but it's still not a great experience.

@jphughan Switching to the RTX2060 in the BIOS allows me to get 2x 4K at 30fps and 1x 4K at 60fps, all through the TB19.  It also enabled me to set my U2718Q to HDR in Windows, which I previously wasn't able to do.  

As you stated, this is causing the cooling fan to stay on constantly, so I'll probably switch back at some point, but it is nice to know that the XPS 17 and TB19 can run three screens correctly and can also output HDR.  

I'm not sure how I feel about HDR on the computer screen, now that I have it.  It may be great for movies and videos, but I'm not sure how I like the changes it makes to Windows and programs.

Thank you again.  I might not stick to these new settings, but I really appreciate you expanding my understanding of how it all works.  

Hello @jphughan . This approach works perfectly with Dell XPS 7590 and WD19TB. But once I connect Dell XPS 9700 to WD19TB using same configuration (usb-c to DB via thunderbolt port and DP to DP via DP port) I am getting 30 fps 4k from thunderbolt connection and 60 fps 4k from DP connection. Can you please help me to resolve this issue? Thank you.

@mesrop.meda93  If you have an XPS 17 9700 with an NVIDIA RTX GPU (not a GTX GPU) and you enabled the BIOS option to have the GPU take direct control of the display outputs, then the XPS 17 9700 supports DisplayPort 1.4/HBR3 over USB-C/TB3.  Without that option enabled (or if you don't have an RTX GPU and therefore the option isn't even available), it supports DisplayPort 1.2/HBR2, just like your XPS 17 7590.

The issue is that the WD19TB allocates video bandwidth differently based on whether the attached system supports DP 1.2/HBR2 or DP 1.4/HBR3.  With an HBR2 system, the source system sends two full DP 1.2 interfaces to the dock, and the dock allocates one interface to be shared among its "core" outputs, and the other interface to the downstream TB3 port.  And since a 4K 60 Hz display requires almost an entire DP 1.2 interface, you have to split them across those outputs accordingly.  With an HBR3 system, the system sends 1.25 interfaces worth of bandwidth to the dock.  Since HBR3 is more bandwidth per interface, the total amount of bandwidth is about the same as the DP 1.2 setup, but this difference has ramifications for bandwidth allocation.  In this case, the WD19TB once again allocates one interface to be shared across its "core" ports, but then there's only 25% of another interface to allocate to the downstream TB3 port.  That isn't enough for 4K 60 Hz even at HBR3 levels.  But that full interface shared across the "core" outputs is enough for dual 4K 60 Hz displays.  So with an HBR3 system, if you want to use dual 4K 60 Hz, you have to avoid using the downstream TB3 port. (If you're wondering why HBR3 systems only send 1.25 interfaces, it works out to 5 lanes of HBR3 since a full interface is 4 lanes -- but 6 lanes of HBR3 would require more bandwidth than Thunderbolt 3, before even considering additional bandwidth required for all of the non-display traffic flowing through the dock.)

If you'll need to switch between those two systems often and you want to keep that BIOS option enabled on your XPS 17, then your most convenient option is probably to get a USB-C to DisplayPort dongle (not cable) for the downstream TB3 port.  When your XPS 15 is connected, keep your 4K 60 Hz display connected through that dongle.  When you want to use the XPS 17, disconnect that display's DP cable from the dongle and plug it into the secondary DP output on the dock instead.

@jphughan I think there is misunderstanding between us. What I'm saying is that when I use Intel GPU as my primary gpu (without switching to NVIDIA GeForce RTX 2060 Max-Q through BIOS) and connect WD19TB with same configuration (TB and DP ports) as it was for XPS 7590 I am not getting 4k 60fps for both external monitors, but once I disconnect docking station and connect it back to XPS 7590 everything works perfectly. But once I mad a change from BIOS to use NVIDIA GeForce RTX 2060 Max-Q as my main gpu I am getting 4K 60fps for both of monitors with same configuration (TB and DP ports). From you answer to my question I understand that this should not happen, that I suppose to get 4k 60fps for both external monitors without changing my current configuration just using my Intel gpu not RTX one. Am I wrong?

@mesrop.meda93  Ok, so you're using the downstream TB3 port and a DP output on the WD19TB for your 4K 60 Hz displays.  And that works properly with the XPS 15 7590.  And now you're saying that on the XPS 17 9700, when you have the Intel GPU as primary, i.e. the BIOS option disabled, then you only get 4K 30 Hz with that cabling setup, but when you enable NVIDIA GPU direct control with the BIOS option, you get 4K 60 Hz?  That is completely opposite of how it should work, so I'm not sure what's going on.  I worked with someone else here about this extensively and they confirmed their XPS 17 9700 behaved exactly like I described in my earlier reply.  If you want to verify that the BIOS option is having the proper effect, open NVIDIA Control Panel and go to the Surround/PhysX section.  In there you'll see a diagram showing which GPU controls which active displays. They should both be on Intel with the BIOS option disabled and both on NVIDIA with the BIOS option enabled.

If the ONLY problem was that you were stuck at 4K 30 Hz when using the Intel GPU, then I would have guessed that this might be yet another case of interoperability issues with the WD19TB, since the XPS 13 9300 had issues running dual 4K 60 Hz through a WD19TB as well.  But I don't understand how it would be possible to run dual 4K 60 Hz when one display is on downstream TB3 and that BIOS option is enabled.  My understanding is that there isn't enough bandwidth available on downstream TB3 in that situation, and again I worked with someone else here who confirmed he had to change his 4K 60 Hz display cabling when he switched this BIOS option back and forth, which again is consistent with the WD19TB's documentation.  So I guess I would initially suggest double-checking your findings, including checking NVIDIA Control Panel.

@mesrop.meda93  Ok, then a few additional questions:

• Did you check NVIDIA Control Panel to verify that the Intel GPU does in fact control both displays?
• While the Intel GPU controls both displays, what happens if you move the TB3-connected display over to the second DP output?  Do you end up with both displays running at 60 Hz or both displays running at 60 Hz?
• If you enable the NVIDIA direct control option and confirm in NVIDIA Control Panel that it controls both displays, what refresh rate do you see when both displays are connected via the DP outputs?  And what do you see when one is connected via TB3?

There are several variables here, so only double-checking and reporting back on one test case does not provide enough information.  If you're using the Intel GPU and only seeing 30 Hz on the TB3 port, then that could be caused by an interoperability glitch where the downstream TB3 display doesn't perform the way it should.

@jphughan I’ve double checked everything and there is no difference. Same configuration and I am getting 30 fps via TB and 60 via DP on Dell xps 9700 with Intel gpu.

@jphughan here are the answers to your questions:

• Did you check NVIDIA Control Panel to verify that the Intel GPU does in fact control both displays?
  • Yes I did. Intel GPU controls both monitors

• While the Intel GPU controls both displays, what happens if you move the TB3-connected display over to the second DP output?  Do you end up with both displays running at 60 Hz or both displays running at 60 Hz?
  • I am not able to do that at this moment, I don't have spare DP to DP cable.

• If you enable the NVIDIA direct control option and confirm in NVIDIA Control Panel that it controls both displays, what refresh rate do you see when both displays are connected via the DP outputs?  And what do you see when one is connected via TB3?
  • I can see 60 Hz on both with TB to DP and DP to DP