U4021QW, M2T102 update, TB3/DP 1.4 issue

@Chris1642  Is DP 1.2 mode that is capable of running 5120x2160 60 Hz a new feature of this firmware release?  The reason I ask is that the only way DP 1.2 could do that would be with two aggregated interfaces.  That's technically possible over TB3 since when TB3 is carrying DP 1.2 video, it has enough bandwidth for two full independent interfaces.  But the reason that surprises ms is that there have been multiple threads about this display posted by Mac users with DP 1.2 hardware who have found that they can't run the display at its native resolution and refresh rate.  They've been puzzled as to why that is given that their Macs are rated to run even high resolution 5120x2880 60 Hz displays.  And my theory to account for that had been that this particular display doesn't support being driven by aggregated DP interfaces and instead requires a single interface, and the only way to run its native resolution and refresh rate over a single interface is with DP 1.3 or better.  So while I can't say for certain why you're having an issue (other than theorizing that mucking around with DisplayPort support might have broken existing functionality) and it's certainly unfortunate that you're dealing with this, I am nonetheless intrigued by your findings because that might allow this display to be used by a broader population of systems.

Thank you for sharing the details, May I ask you to check with another external monitor if available? As that could tell us where the problem lies, do let me know if this is possible to be tested?

Well that's where it continues to be weird....I too, thought that even if the DP 1.2 did somehow fix it (i was desperate), I'll lose the 60hz....but sure enough, it instantly fix the constant and off - and yet I stay at 60hz with 5120x2160. 

However, my wife's XPS 9380, which is TB3 but DP 1.2, it still is only showing 30hz. 

So I have no idea why the firmware messed with the specific combination of TB3/DP 1.4 with my XPS 7390 2in1. This is on two monitors now, so it wasn't a firmware update issue like I originally thought. When I disable TB altogether, the DP 1.4 mode works fine on the monitor. Yet, with the same thing you mention (hoping it was a hidden new capability), when at DP 1.2, my Wife's XPS 9380 TB3/DP 1.2 still works at a max of 30hz. In another theory, I thought maybe the DP 1.2 mode of the monitor is defaulting away from the TB aspect of the port, and just using USB-C tech from my laptop (making it start working again), but at least according to the Dell Thunderbolt App, it shows the monitor plugged in as if it is still using the TB technology. So while I'm happy I found a fix that doesn't really affect anything I do (setting the DP 1.2 mode seamlessly changed nothing for me), it's still a weird solution.

I'd like to try another TB3 laptop with DP 1.4, but sadly don't have one to try. 

Thank you for checking that out, I am going to have this checked with the product specialist once & see if they have any solution for this. Before that I would need few details here.

Can you please let me know what is the Windows Version we have on your computer?

What is the video driver version from the device manager?

Another monitor works without issue with my laptop, as well as my wife’s. Also, using another monitor via the TB16 Dell dock with my XPS 7390 2in1 also works without issue.

The *possible* difference in those 2 specific situations: the other monitor is not a TB/DP1.4-only monitor…..and the Dell TB16 requires TB3, but not DP1.4. It allows TB3 with DP 1.2 and DP1.4.

Both more pointing to the specific combination of the TB3/DP 1.4 and this new firmware on the U4021QW.

@Chris1642  My only theory there is that maybe older Intel GPUs don’t support DP link aggregation to achieve dual DP 1.2 to drive that display, whereas your newer XPS 13 does. But single DP 1.2 can’t run 5120x2160 60 Hz. And if you were using USB-C, then you‘d only have half of a DP 1.2 link if you were also running USB 3.x data, so that would be worse.

In the first U4021qw I had, and this new one: it is Intel Iris Plus Graphics, driver version 27.20.100.9664, dated 6/1/2021. 

As far as Windows, with the initial u4021qw monitor, I had Windows 10 Professional. Since getting the replacement u4021qw, I have done a full clean install of Windows 11, currently at version 21H2. The HDD was wiped and installed fresh. Essentially, same issue on both Windows versions. 

I should relay that technically, leaving it on the DP 1.2 setting has fixed all my issues - but it's just very odd that the moment I updated the firmware on the Monitor, the default monitor's DP 1.4 setting will not work using the TB3/DP 1.4 port. I have tried moving it back to DP 1.4, while connected and it working in the DP 1.2 setting - and the issue instantly starts again....so it's very specific to the TB3/DP 1.4 setting with my 7390 2in1, only when the firmware updated. 

But hey - the KVM fix works wonderfully as well now!

Yeah, that's where it's weird that switching the monitor to DP 1.2 should make my 60hz stop working with the 7390 2in1, but instead....it solves the issue, while retaining the 5120x2160@60hz. 

and this is only after the new firmware was updated, now on two monitors. It is either specific to TB3/DP 1.4, or more likely a combination of that + something with my 7390 2in1. 

Thank you for providing us more insight of the issue,, we have escalated this to our product specialist, we would need to check if the issue is working as expected or if there are any limitations, we may be able to get an update in the next 3-5 working days, we shall keep you posted as soon as we have updates from them. 

I should add that using a non-TB laptop (Lenovo Yoga 6, Ryzen 7 5xxx series) with basic USB-C/DP 1.4 works without issue with the monitor set to either DP 1.2 or DP 1.4, both at the full 5120x2160@60hz.

More just clear that the Monitor TB port being set at DP 1.2 doesn't really 'limit' it to only DP 1.2 bandwidth, but somehow fixes my issue post-FW update issue. 

Hi, We’re still awaiting an update from our product engineering team. We’ll write to you as soon as we hear from them.

No worries. Like I said, keeping the TB3 port in "DP 1.2" mode resolves my issue and keeps the full resolution and 60hz....more posted this if someone had the same issue after the update. It's just so weird to be specific to my 7390 2in1. However, I have yet to be able to test another TB3/DP 1.4 laptop. I have only tested a USB-C DP 1.4 laptop and a TB3/DP 1.2 laptop. Both had no issue with either 'mode' of the monitor. 

Alas, hope someone else with the issue sees this message for the quick fix - or maybe there will just be a fix with a firmware/driver update. Who knows! Thank you for the regular updates. 

Hi There,

Thank you for the details, as this is under the escalation for our next level to review and assist further, looks like they would need a ideo clip for them to understand the issue better. Are we able to take a video clip of 1-2 minutes recorded and shared to us through a external cloud sharing link like google drive or imgur etc.?

Hi There, We see that you had contacted us recently regarding issues with your computer, and our experts have been waiting for your confirmation on the outcome of the suggested steps/ provide the requested details, this service ticket is currently in-progress. Please reply to this message, so we can keep you posted with further updates on the service status.

I will be posting a video. Looks like I am not alone as well. Someone else just posted the same issue with a Lenovo laptop, as well as trying a MacBook Pro M1, on Reddit.  All was working until they did the firmware update. Since this happened to me with 2 monitors, + others, it’s likely specific to this new firmware.