Latitude 7400, U2719DC, Daisy chain, second resolution issue

@LW_MVEE  what specific cables and display inputs are you using for setting up your daisy chain?  The U2719DC is a QHD/2560x1440 display, so if you want to run two of them off a single output from that system, you need to use a USB-C to DisplayPort cable to connect your laptop to Display #1, not a regular USB-C to USB-C cable.  The reason is that when you use the display's USB-C input, most displays (including the U2719DC) set the USB-C interface up to carry USB 3.x data along with video.  That's convenient, but carrying both USB 3.x data and video means you only get half the video bandwidth you otherwise could, and that's no longer enough for dual QHD displays from that single link. Of course switching over to USB-C to DisplayPort instead of USB-C means you'll lose the ability to charge your system through that cable as well.  If your system supported DisplayPort 1.3+, which adds a higher bandwidth HBR3 mode, then you'd be able to send enough video bandwidth for dual QHD even over a USB-C link that was also carrying USB 3.x data -- but the Latitude 7400 only supports DisplayPort 1.2, which only supports up to HBR2 bandwidth, because the Intel GPU in that system doesn't support anything newer.  The only Intel GPUs that support anything newer are the ones in the brand new "Ice Lake" CPUs, which are the 10th Generation Core CPUs that have a "G" in their name.  Confusingly, there are other 10th Generation Core CPUs that use a refreshed version of the 9th Gen architecture and do not include the newer GPU to add this capability.

Hi LW_MVEE, I believe you are trying to connect 2 monitors to your latitude laptop, and the concern is one of them is giving you high definition resolution and the other is not, though there are a lot of articles to check and resolve the issue https://dell.to/2nLQGpx. We would like to know if swapping the cables does that make any difference with the resolution, the resolutions might be affected depending on the monitor maximum supported resolutions, however, considering the quoted display that shouldn't be a concern either.

Have they worked before, are we using a docking station for these multiple monitor set up. Could you tell me the cables that are used and if there are any adapters being used, as even they could affect the resolution out put. 

Cables used are USB-C to USB-C that was delivered with U2719DC and the daisychain is connected with DP to DP that was also included with U2719DC.

As mentioned in other posts the dual 27" daisy chain was tested with similar program. We tested with 2 different 24" displays both 1920x1200. One supporting DP 1.2 and the older one DP 1.1. I was requested to provide service tags via private message - which I did.

Main reason to ask this is that the older Dell Latitude was able to present correct resolution for both displays with same intel 620 graphics but a newer Latitude didn't. No dock is used to benefit the Powershare feature of the U2719DC

Would it be a possibility to upgrade display firmware as such that user can select between usb 2 and usb 3.x, since the connected devices are mostly keyboards and mice and thus providing more bandwidth for GPU?

@LW_MVEE  in addition to the reply I just posted, take a look at the U2719DC manual here.  Page 30 includes the following:

NOTE: The maximum number of supported U2719DC via MST is subjected to the bandwith of the USB-C source. Please refer to “product specific problems –No image when using USB-C MST".

If you click that link in the manual, you'll jump to Page 52.  The bottom item in that troubleshooting table relates to the second display not showing an image or not in "Prime mode", which apparently means "native resolution".  The fix is listed as this:

Go to OSD menu, under Display Info check the Link Rate is HBR2 or HBR3, if Link Rate is HBR2, suggest to use USB-C to DP cable to turn on MST.

As I originally said, your laptop only supports HBR2 mode because all Intel GPUs except the new Gen 11 GPUs introduced with the 10th Generation "Ice Lake" CPUs are limited to HBR2.  That means you can't run dual QHD when you have a USB-C to USB-C link to Display #1 unless Dell provides a firmware update that allows you to have the display only carry USB 2.0 over that link.  Until then, if you want to use a daisy chain setup, you'll have to use a USB-C to DP cable as I suggested above and as is suggested in the manual.  I personally wouldn't count on a firmware update like that appearing, though.  The U2719DC already supports HBR3, which means that if you had an HBR3 system, you could run this daisy chain setup using USB-C to USB-C even with USB 3.x data being carried over that link.  Of course that doesn't help HBR2 systems, and it would be NICE if Dell had a "compatibility mode" for daisy chaining with HBR2 systems, but again based on my experience I wouldn't count on that happening.  If Dell wanted to do it, they probably would have done it from the beginning, and the more time goes by, the more HBR3 systems will arrive on the market, which means less need for this type of update.

@LW_MVEE  in theory yes Dell could offer a firmware update to allow the choice between using all high speed lanes of the USB-C interface for video, and therefore supporting only USB 2.0, or using half of the high speed lanes for video and the other half for USB 3.x.  Dell's own U4919DW Dual QHD display permanently operates in USB 2.0 over USB-C because again, with DisplayPort 1.2/HBR2 systems, that's the only way to get the required video bandwidth to that display over USB-C.

I'm not sure what you mean when you say, "As mentioned in other posts the dual 27" daisy chain was tested with similar program."  This isn't a program-specific limitation.  It relates to the capabilities of the laptop and the cabling you're using.  If you were able to run dual 27" displays via daisy chaining even while the first display was connected over USB-C, then are you sure they were 27" QHD displays?  There are 27" 1080p displays, and dual 1080p via daisy chaining works fine even when you're using USB-C to the first display and carrying USB 3.x, because dual 1080p can be carried within the available video bandwidh in that setup.  That's also why your dual 24" setup worked fine.  But if you were able to run dual QHD displays via daisy chaining while connected to the first display over USB-C, then there are only 2 ways that would have been possible:

• The first display in the chain only carried USB 2.0 over USB-C, thereby keeping enough video bandwidth over USB-C to support dual QHD.
• Both your source system and the first display in the chain supported DisplayPort 1.3+/HBR3, which would allow enough bandwidth for dual QHD even if USB 3.x data was also being carried over USB-C.

The GPU isn't the most important factor here.  Intel GPUs for a few years now have supported up to triple 4K displays as long as you have the right ports and cables to run that setup.  So yes, older Latitude systems can certainly run dual QHD, but you still have to connect the displays in a way that allows the system/GPU to actually transmit the necessary bandwidth to run that setup.

But unless you get that firmware update you asked about, the only way to run dual U2719DC displays both at QHD resolution from that system AND receive power all from a single cable would be to use a Thunderbolt dock such as the Dell WD19TB.  That will charge your system, and then you can connect each U2719DC to a DisplayPort output of the dock.  Note that the regular WD19 USB-C dock would not tap into enough bandwidth to run dual QHD from that system.  It would have the exact same problem that the display itself is having becuase it would attempt to carry USB 3.x data and video over its connection to your laptop.  The WD19TB Thunderbolt dock has access to 4x more display bandwidth than the WD19 on that system, so it could actually run dual displays up to 4K.

Thanks for the reply!

I mispoke and with "Program" meant Setup and I'm certain that WQHD was used as a main display.

Is there any way to improve the chances for firmware update to happen? We mostly use Dell in the company but we are still far away from the new gen10 cpus. The reason to use powershare display was to avoid using WD15/WD19 which we already do. 

@LW_MVEE  well if WQHD was only used as the main display, it's possible that the setup allows enough bandwdith for one WQHD display and one FHD display.  I've never tested that, and Dell's documentation about multiple displays assumes you're using the same resolution and refresh rate across all of them.  It would be nice if the documentation basically said, "When you use this type of cabling, you have this much bandwidth available.  Below is list of the bandwidth requirements for all of the common display resolutions.  You can figure out whether your intended display setup will work by doing the math."  But that's not what they've done.  Anyhow, in terms of getting a firmware update, if your company has a Dell account rep, I would definitely start there.  Then I'm told that the DellCares and DellCaresPro Twitter accounts are actually fairly responsive.  That doesn't necessarily mean that they'll be able to deliver on this, since that would of course require more effort from more people, but you never know.

And just as a side note, be aware that not all Gen 10 CPUs have the new GPU.  Intel has made their confusing processor naming even more confusing by using "10th Generation" branding for two completely different lines of CPUs.  The first are the CPUs built on the new "Ice Lake" architecture I've mentioned, which uses a new 10 nm fabrication process that gives them significantly better performance and power efficiency (and therefore lower heat and better battery life), and they also include a new and much more capable "Gen 11" GPU that supports things like HBR3.  But there are other 10th Gen CPUs that use the "Comet Lake" architecture, which means they're still on the 14 nm fabrication process and do not have the Gen 11 GPU.  That architecture is just a minor refresh of the 9th Gen architecture, which in fact has just been a series of minor refreshes going all the way back to 5th Gen (Broadwell).  Until Ice Lake arrived, Broadwell was the last truly significant architectural redesign.  As of this writing, the Ice Lake CPU models have a "G" followed by a number at the end of their name.  The higher the number, the faster the GPU, but they're all Ice Lake and even the G1 CPUs have GPUs that support HBR3.  If you ever want to check for sure, ark.intel.com is a great resource for seeing detailed specs on CPUs, and it's becoming even more indispensable as Intel continues to expand their model lineup and use the same "branding" for completely different things.