Demystifying Dell WD19TB supported display resolutions

Hey @AdamL242, glad you've found this thread useful!  And thanks very much for the kind words.  Always gratifying to hear that people are benefiting from these types of posts!

I don't have experience with the P52 specifically, and there is always the potential for firmware glitches to cause setups that are SUPPOSED to work on paper not to ACTUALLY work in reality.  I've seen multiple occurrences of that with Dell's WD19 dock family models already, and the fact that you needed a firmware update to use the third display at all is another example.  (And new firmware updates only just resolved some glitches I've been dealing with on Lenovo USB-C and Lenovo Thunderbolt 3 docks since I bought them almost two years ago!)

Anyway, a triple QHD setup with one display on the downstream TB3 port should be valid for both HBR2 and HBR3 systems.  But if that isn't your experience with the P52, then since it does seem quite likely to be an HBR3 system based on that GPU and that NVIDIA Control Panel readout, I would suggest trying one of the other valid cabling options for triple QHD with an HBR3 system.  You didn't specify which outputs you're currently using on the WD19TB for the displays that aren't on the downstream TB3 port (and it's not clear from NVIDIA Control Panel since it wouldn't know which dock output was in use), but if you haven't already, try running two of the displays via the DP outputs on the WD19TB and put the third display on the USB-C port near the HDMI output since you've already got the right type of cable for that plugged into the downstream TB3 port.  Or you could use the two DP outputs and the HDMI output if you had an HDMI cable.  Note however that you can't use the HDMI port and the nearby USB-C port simultaneously due to a limitation with the dock.  Those cabling setups should all be valid for triple QHD with an HBR3, although they wouldn't be valid for an HBR2 system, which I realize might be an issue if you're setting up a "hot desk" where different people with different laptop models might be using it from one day to the next.

Other than that, have you checked the Lenovo Vantage app to confirm that the P52 is current on its BIOS, TB3 controller firmware, and NVIDIA drivers?

And in terms of the "4 lanes", somebody might have been referring to PCIe lanes.  The TB3 spec mandates PCIe x2 and leaves PCIe x4 as optional (TB4 makes PCIe x4 mandatory), and some users mistakenly believe that video bandwidth runs over PCIe.  In reality they are completely separate, and therefore video and PCIe capabilities of a given system's Thunderbolt port are completely independent of each other.  (And if you've found this thread useful, I've got another explainer post here about the various operating modes of USB-C and TB3, with specific focus on their impacts to possible display setups.)

@AdamL242  Great news!  Glad I was able to help.  In terms of other cabling configurations that should be valid for triple QHD on both HBR2 and HBR3, the key is normally to have one of the displays on the downstream TB3 port, because that port has at least enough bandwidth for QHD with both types of systems, and the remaining outputs between them have at least enough output for dual QHD with both types of systems.  So in theory, any combination that involves at least one display on downstream TB3 should work, EXCEPT for HDMI + USB-C.  Good luck!

Thanks @jphughan ... you've done it again; your simple suggestion of moving a single cable a few centimeters from downstream TB3 to the USB-C output on back (non-TB) was all that was required to get 3x QHD from a Lenovo P52. 

I feel it's like the equivalent of turning it off / turning it back on again... could have sworn I'd already tried it, but seeing you spell it out made me be very sure to test it carefully.

Definitely validation that the WD19TB dock runs expected 3x QHD on the Lenovo P52 I'm palping.  It was just that specific configuration I tested which didn't seem to work for me.

In summary... the manual's Display Resolution Table says the cabling configuration I was using (DP + DP + downstream TB) should support at least 3x QHD on both HBR2 and HBR3, however my Lenovo P52 (HBR3) didn't support it.

There are a couple other cabling configurations in the Display Resolution Table that seem like they're the same for at least 3x QHD on both HBR2 and HBR3 devices... going to rustle up some cables to try them out!

Hello,  I searched this thread but could not find an answer to whether the WD19TB can support dual 5120x1440 monitors.  I assume that because it can support dual 4k display (4k is considered to be higher resolution) it should be able to support dual 5120x1440,  

However, the official response that I have gotten from Dell Tech support told me the following:

"I reached out to my L2 team to review, and they determined 5120x1440 was not a supported resolution for the Dock."

And on the contrary to Dell Tech support statement I have tested this and am able to display both  monitors @ 5120x1440 from my WD19TB docking station, however, I am getting some wonky behavior. 

For example, when I wake the computer from sleep one of the monitors will downgrade resolution to 2560x1440 while the other will remain at 5120x1440. The quick fix is to unplug the docking station and plug it right back in and both monitors are back to 5120x1440 resolution.

Another thing to mention is that I just updated the firmware of the wd19tb and am doing further testing to see if there is any improvement.  I've also enabled the Nvidia Graphics card in the bios.  The intel Graphics firmware is up to date.

The monitors are connected via 1 HDMI and 1 full size DP 1.4.

Is there anything else I should consider so that I can run these monitors without buggy behavior?

@alexcapone  I'm not too surprsied by that answer from Dell Support. The dock documentation doesn’t take into account “specialty” displays like ultrawides or high refresh rate displays, and if it’s not mentioned in the documentation, then Dell Support will probably tell you it isn’t supported or just plain won’t work.  Or maybe they confused “5120x1440” with “5120x2880”, the latter of which IS mentioned in the documentation, but which is also a completely different display setup.

Anyhow, as you say, 5120x1440 is slightly less total pixel area than 4K, so dual 5120x1440 should indeed work.  In terms of why it doesn’t ACTUALLY work quite as it should, it may well be a still-unresolved glitch in firmware or drivers.  As one slightly related example, the XPS 15 9500 used to have a bug whereby it would hang at startup if a display with specifically 5120x1440 resolution was attached at startup, either directly or through a dock.  That was later fixed with a BIOS update.

In terms of things you may be able to do about it, you didn’t mention what system you’re using at the moment, but if you’re using the DP and HDMI outputs and both displays are currently running at 60 Hz, then that suggests you’re using a system capable of DisplayPort HBR3.  In that case, you wouldn’t be able to use the downstream TB3 port on the dock for one of your two 5120x1440 displays.  But you could try other output combinations, such as using the two DP outputs.  Or if you’re using DP+HDMI because one of your displays only has HDMI, try DP and the USB-C output near the HDMI output by a USB-C to HDMI 2.0 cable/adapter.  Obviously that shouldn’t be necessary, but when dealing with problems that shouldn’t exist, sometimes changing things that shouldn’t matter turns out to matter.  And fortunately, a USB-C to HDMI 2.0 cable/adapter isn’t expensive, or difficult to find, or difficult to return if it doesn’t solve your issue.

@alexcapone  Happy to help. The XPS 17 9710 is a DisplayPort HBR3 system even if you do NOT have that option for the NVIDIA GPU to have direct control fo the outputs enabled.

If you want to try HDMI to DP (assuming you mean HDMI input on the display to DP output on the dock), make sure you get an active adapter, not the much more common passive adapter. The reason is that passive adapters would rely on the DP output supporting “Dual Mode DisplayPort”, which allows the DP output to send a native HDMI signal. The dock supports that, but I don’t think it will support HDMI 2.0 signaling, which you would need for 5120x1440 60 Hz. The fact that the DP output can run that setup in native DP mode does not mean it can do that in HDMI mode. By comparison, an active adapter would allow the DP output to continue sending a native DP signal, and then the adapter itself would contain a chip that would switch that to HDMI. However, if you’re finding that the display attached via DP is the problematic, I kind of doubt that continuing to use it and simply adding an adapter will improve things, since from the dock’s standpoint it will still be sending the same type of signal that will simply be converted downstream inside the adapter.

On the other hand, the dock does not allow you to use the HDMI output and the nearby USB-C output simultaneously, so that port combination wouldn’t work. That’s why I suggested DP + USB-C or even DP+DP if your displays allow that. You might find that even if the DP output is the problem right now, switching the output used by the other display could affect it in a positive way.

Thank you for your thoughtful response. I'm using a Dell XPS 17 9710 with Nvidia 3060 graphics card which has been enabled in the Bios.

I will try various combinations of cables and see if anything sticks. Surprisingly HDMI is the most stable output.  The DP 1.4 output is what has the downgraded resolution.  

Perhaps its worth trying 1 HDMI + HDMI to DP adapter.  Will test and revert.

Thanks @jphughan for the heads up on the active adapter.  I am not familiar with these things so this is very helpful.  Just a question on this statement:

@alexcapone  Happy to help. The XPS 17 9710 is a DisplayPort HBR3 system even if you do NOT have that option for the NVIDIA GPU to have direct control fo the outputs enabled.

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I am not sure if I fully understand this comment or the implications of it.  As mentioned, I have enabled the Nvidia 3060 graphics card in the BIOS.  In the Nvidia control panel I am able to control the settings for each monitor, however that does not prevent the resolution from downgrading to a lower resolution when waking the laptop from sleep. 

I should note that in my testing I noticed that when the discrete graphics card was enabled the downgraded resolution was still higher vs the integrated graphics card when resolution was downgraded.  

Also, I forgot to mention one other point.  In my testing the only set up that never fails or is buggy is when  one monitor is connected to the wd19TB via HDMI and the other is connected directly to the laptop via thunderbolt port using a DP to USB-C cable.  The only downside to this is that I need to connect two cables to my laptop.  Although it works I am trying to find a way to achieve this reliability with the single wd19tb cable.

@alexcapone  Happy to help.  In terms of the question you have, the BIOS option doesn't control whether the discrete GPU is enabled.  It controls whether it has direct control of the outputs.  If you do NOT enable that setting, then the Intel GPU will control the outputs, but the NVIDIA GPU will still be used when needed as a "render-only" device.  So basically it will do the hard work and then pass completed video frames to the Intel GPU to pass through to the displays.  If on the other hand you enable the option for the NVIDIA GPU to have direct control of the outputs, then this passthrough won't occur, but it also means the NVIDIA GPU will need to stay active whenever displays are connected, even if nothing graphics-intensive is going on.  This can result in more heat, fan noise, and battery drain (if using external displays while not connected to a power source).

But my point was that on the XPS 17 9710, both the Intel GPU and the NVIDIA GPU support DisplayPort HBR3, so the video bandwidth available to the dock and the way the dock allocates that bandwidth across its outputs will be the same regardless of which GPU controls the outputs.  On the XPS 17 9700, the Intel GPU only supported DisplayPort HBR2, while the NVIDIA GPU supported HBR3, so the system could behave differently depending on whether that BIOS setting was enabled.

But given that you have a DP to USB-C cable available for testing, have you tried the setup of connecting one display connected to the DP output of the dock and the other display connected to the USB-C output of the dock (the one near the HDMI output) using that DP to USB-C cable, rather than using that to connect directly to the system?  Do you have the necessary cables to test that combination together?

I've just tried DP to USB-C + DP and at first I was experiencing constant jittering on the second monitor but I noticed that both monitors were refreshing at 120hz in the Nvidia Control Panel.  Once I changed to 60hz for both monitors it seems to be a promising solution.   I still need to do further testing (restart, lock/unlock, wake from sleep, etc) to test the behavior in various scenarios.  Another thing, I did was create a monitor configuration profile in Display Fusion so that the settings are "remembered" and I can quickly fix things if anything is out of whack:

Assuming this is a stable solution I did have one more question.  I wanted to buy some Fluance speakers which have USB-C connection for PC.  Can I connect it to the regular USB-C port in the front of the wd19tb or does audio need to be connected to the USB-C multi-function Display port?  If the latter is true I need to see if another cable combination works for the monitors so that I can free up that USB-C multifunction display port.

Thanks @jphughan 

So just a follow up to my last post.  After coming back to my desk and trying to wake my computer from sleep it seems that both monitors defaulted to a horrendous 640x480 resolution and the only fix was to unplug from the laptop and replug and both monitors were back to 5120x1440.  I can't even change the resolution in the display settings to fix it as it tells me that 640x480 is the maximum.  Display Fusion couldn't correct it either, unfortunately.

So it seems the sticking point in the cable combos I've tried so far is that it doesn't remember or cannot display maximum resolution unless I unplug and replug back into the laptop.  The only cable that has not downgraded the resolution after waking from sleep is the HDMI cable.  Once I get that HDMI to DP active adapter I am going to try to see if HDMI + HDMI to DP will solve the problem.

@alexcapone  Glad to hear you're making progress.  Although you're saying that when you had both displays connected through the dock, both were initially running at 120 Hz?  Dual 5120x1440 120 Hz doesn't seem possible from a bandwidth standpoint given what's available over Thunderbolt, unless maybe DisplayPort DSC was in use, but I'm not sure if that would have been the case or even would have been available, since I haven't yet delved into that enough to understand what devices in a dock scenario have to support DSC in order for it to be used. (For example, can a dock that supports it use it and then decompress the signal for a display that doesn't support it? Or can a dock that doesn't support it still pass it through to a display that does?  I just don't know.)

Still, dual 5120x1440 60 Hz should be achievable, so I hope that turns out to be a stable setup.  In terms of USB speakers, they're pure data devices, so you can certainly connect them to the USB-C port at the front of the dock.  You might even be able to use a female USB-C to male USB-A adapter if you want to keep that connection at the back of the dock, unless the speakers are designed to take advantage of the extra power available that's typically over USB-C and not over USB-A.

With regards to DSC, 

I just tested it with the WD19TB and it seems to actually support DSC (could drive 2xUHD@60 + 1x3840x1600@120 all on the MST-Side).

This fits with the specifications of the actual chip doing the work (Synaptics VMM3550, specs: https://uploadcdn.oneyac.com/attachments/userfile/b4/13/1593672494627_4765.pdf)

And this specific chip can pass-through DSC arbitrarily and decompress display data for every one of its SST outputs separately.

But as far as I understand it, since Displayport is packet-based, I actually would expect pass-through to work through any MST-Hub, even old ones, predating the specification of DSC. But I do not have the HW to confirm this.

Also, DSC still works on the WD19TB, when the TB-Out is used as display output (HBR3 in my case) and the MST-Hub should only be getting a slower connection. DSC still allowed the Dock to run an additional UHD@60 display of the MST side.

@alexcapone I too saw instability issues, when maxing out the compression. 1 or more displays went dark and where regognized again after a few seconds (just like reconnecting). After a few of those I also saw it limiting bandwidth or no longer recognizing a monitor. For me, this seemed to be more or less proportional to amount of compression that was needed (compare with Dells specs, which only give resolutions possible without any compression).

@Ray519  That's great information on all fronts.  Always helpful to see real world tests since sometimes tech can perform above or below specs due to unadvertised/untested capabilities or firmware glitches.

I would expect DSC to pass through MST hubs and such as well, but I've also learned that not everything that SHOULD work in the tech world always DOES work.  And if the display itself doesn't support DSC, then of course passthrough capability would not be useful.

Sadly I have a feeling that while DSC will enable some high-end display setups, it will also make spec sheets and support tables quite a bit more complicated.  There are already separate tables/rows for things like Thunderbolt vs. regular USB-C DP Alt Mode and then for DisplayPort HBR2 vs. HBR3 support, the latter of which often isn't even clearly advertised in the specs of the system.  But now with DSC, I imagine there will have to be at least one new table based on whether the user's system supports DSC.  But even that will require some sort of caveat saying that you'll either need displays that support DSC natively or an intermediate dock/MST hub that can unpack that DSC signal for them -- which will of course send users down a rabbit hole of figuring out whether DSC support is available on those devices.  And then what if your dock/hub doesn't support unpacking DSC and only certain displays you have support DSC?  Will there be yet another table for "partial DSC support"?

I do sympathize for the everyday user who just wants to know if a given set of equipment will allow them to run a given display setup....