Dell XPS 15 9500 - DP1.4 output?

@M3LPL  One quick additional thought.  The XPS 15's only direct competitor in the PC space is the ThinkPad X1 Extreme.  On that system, the USB-C/TB3 outputs are wired to the discrete GPU, so it does support DP 1.4 -- at least as of the Gen 2 model that I have, where I have confirmed this via testing.  The Gen 3 model was just released, and for the first time it can be ordered with only an Intel GPU.  In that configuration, you'd only get DP 1.2, but Gen 3 models that have a discrete GPU still support DP 1.4.  Given that Dell completely changed the port layout of the XPS 15 with the new 9500, these two systems aren't as directly comparable as they used to be, since the X1 Extreme still has a broader variety of ports (and more ports overall), but I figured I'd mention it as an option if you didn't already have the system but still wanted that type of system with the ability to run 5120x1440 at 120 Hz.  I was actually disappointed with Dell's decision on the XPS 15 9500's port design, which prompted me to write up a comparison thread here if you're interested.

Wow - Thanks you for your response!

the specs of the XPS 17 9700 only mention DP 1.2 support, even though configurations that include an NVIDIA RTX GPU have a BIOS option that allows the NVIDIA GPU to have direct control of the outputs, in which case DP 1.4 is supported

That's a very valuable hint. Do you happen to know whether that option exists on XPS 15 9500?

As an alternative, I've been also looking into Razer Blade 15 laptops, but they also don't mention any specific details about the thunderbolt architecture on their systems, and the support doesn't seem to understand the issue. I found that such an option existed on some 2018 models but I can't assume this is still the case. If anyone owns a 2020 model of Blade 15 (basic/advanced) could confirm that 1. this is still an option 2. the thunderbolt controller on the motherboard supports HBR3 (Titan Ridge series) I would be very grateful.

@M3LPL  Multiple XPS 15 9500 owners have confirmed that it does NOT have the BIOS option I described on the XPS 17 9700.  In fact, since the XPS 17 9700's BIOS option was discovered, it's become clear that it's only available specifically on systems with an NVIDIA RTX GPU.  XPS 17 9700s with an NVIDIA GTX GPU do not get that option.  That isn't mentioned in the documentation either, and it's come as quite a disappointment to people who were hoping to use their GTX-based XPS 17s for things like VR and G-Sync.

I'm not too surprised that Razer's support team doesn't get all of this.  Dell Support doesn't either, judging by some of the answers that people have gotten.  (In fact, in just the past week here, I've seen posts from two different XPS 13 about answers they got from Dell Support.  One was told that the XPS 13 can only run a 4K external display if it was configured with a 4K built-in display.  The other was told that since the XPS 13 is a "high-end system", it can only run external displays at all through a "high-end full dock" and cannot do so through a basic USB-C to DP/HDMI cable.  Both of those claims are completely false.)

But one important point to understand is that Titan Ridge does not guarantee DP 1.4/HBR3 support.  Titan Ridge is necessary for running DP 1.4 over Thunderbolt 3, but it isn't always sufficient.  If the GPU itself doesn't support DP 1.4, then having Titan Ridge isn't going to add it.  And that's the problem with the XPS 15 9500.  It has a Titan Ridge TB3 controller, but it still only supports DP 1.2 because of limitations at the GPU at the beginning of the chain.  Additionally, since Titan Ridge is a Thunderbolt 3 controller, it only comes into play when actually using TB3.  When using regular USB-C DisplayPort Alt Mode, it's not involved at all.  So in that setup, it's possible to have a system that supports DP 1.4 without supporting Thunderbolt at all -- like some recent Microsoft Surface products, for example.  If you'd be using a USB-C to DisplayPort cable to connect your system to your display, you'd just be using DP Alt Mode, so the Thunderbolt 3 controller generation would be irrelevant in your case.

The major question you need to ask is which GPU the USB-C/TB3 display outputs are wired to.  If you actually have a system or can get in touch with an owner, the way to test is to connect a display to the port you want to test, then open NVIDIA Control Panel and go to the "Configure Surround/PhysX" section.  In there you'll find a diagram showing which GPU controls each active display.  See which one controls your display when it's connected to the port you want to test.

Once again - thanks for the extensive response. That makes perfect sense.

I noticed that the XPS 17 9700 user's guide contains weird information:

https://topics-cdn.dell.com/pdf/xps-17-9700-laptop_users-guide_en-us.pdf

This part refers to all 4 USB-C ports:

> Supports USB 3.2 Gen 2, DisplayPort 1.4 (supporting up to HBR2), (...)

This seems contradictory to me - or is it actually "compatible with DisplayPort 1.4" but really just DP1.2?

Sorry to be bombarding you with so many questions - it seems I have no other way to determine whether this machine will work for me otherwise. One more thing is still not clear to me - in the case of XPS 17 9700 with RTX graphics, if I were to enable the option for the RTX GPU to control the display output, does it switch one of the USB-C ports to DP Alt mode and bypass the TB3 controller altogether, or does it just connect the DP output of the RTX GPU to the TB3 controller?

It seems to me that in the first case (where the controller is bypassed), it is mandatory to connect the display via a USB-C to DP cable, which means connecting the display via a dock is out of the question. Is that correct?

If so, how does this work with the XPS 17 having 4 USB-C ports? Is one of them specifically designated as the RTX GPU output? Does it get assigned as one dynamically? Does it disable the TB3 on all of them?

@M3LPL I've never seen a system that supports DisplayPort 1.4 but only HBR2.  HBR3 support arrived with DisplayPort 1.3, and my understanding is that it was mandatory to claim support for the spec, but maybe that isn't true.  The additional wrinkle though is that I distinctly remember helping someone set up an XPS 17 9700 with a Dell WD19TB dock.  That was a useful testing/experimentation exercise because the WD19TB can support dual 4K 60 Hz displays over Thunderbolt 3 regardless of whether the source system is running HBR2 or HBR3 -- but it allocates display bandwidth differently based on which mode is being used, which affects the combinations of ports that you can use to run dual 4K.  (I wrote a long "Demystifying WD19TB" thread about that here a while back.)  Anyhow, the OP of that thread was having trouble running dual 4K 60 Hz because they were using the wrong combination of ports for an HBR2 system.  But after I fixed that, we kept talking, and he found this BIOS option.  When he enabled that, suddenly he had to use a combination of ports valid for an HBR3 system to run dual 4K 60 Hz.  So that real-world testing would seem to indicate that the XPS 17 9700 does in fact support DP 1.4, with HBR3, at least when that BIOS option is enabled.  But the documentation you linked doesn't mention that BIOS option at all or that it's only available for RTX GPUs.  More interestingly, I distinctly remember that the documentation USED TO mention only DisplayPort 1.2.  So maybe somebody is trying to correct things and hasn't gotten it quite right yet.  (I do sympathize with regular users who ask how they're ever supposed to figure all of this out in terms of DisplayPort revision levels, allowed port combinations being different depending on DisplayPort revision in use, inability to find that information in the specs in many cases, and now not even being sure that the information in the specs is accurate when it's available at all.  Sigh...)

Anyway, that BIOS option would not bypass the Thunderbolt 3 controller.  It would just mean that the RTX GPU would be running the DisplayPort interface wired to that port, whether it's going directly to the port or through a Thunderbolt controller.  This option is also found on the Precision 7000 Series models (at least some of them) and the way it works is that the outputs and Thunderbolt controller are wired back to DisplayPort multiplexers, and then those multiplexers are wired back to BOTH of the GPUs in the system.  The BIOS option chooses which of those paths between multiplexer and GPU is active.  So the "switch" occurs upstream of the TB3 controller (if used) and the USB-C port (if not used).  As for whether or not TB3 gets used, all four ports on the XPS 17 9700 support Thunderbolt, but they'll only actually USE Thunderbolt when connected to a Thunderbolt device.

In terms of how many total interfaces are available from the GPU to run displays simultaneously, I'm not sure, and that question can be hard to answer.  If you're up for a LOT of reading, I wrote a long explainer post about this concept here -- but it doesn't contain a firm answer specifically for the XPS 17 9700.  It just explains how it all works and what the ramifications are.  My guess here is that the RTX GPU would support at most 4 simultaneous independent displays, and the built-in display would count as one.  But in addition to bandwidth limitations that might exist depending on the displays you wanted to run, there might be further restrictions in terms of which ports you can use simultaneously based on how many actual interfaces are available from the GPU to the ports.  I just don't have a way to know that, since this isn't something I've ever seen published in laptop specs (probably because it would become incredibly confusing to many people), nor have I seen any real-world testing that would answer this question.

I have a brand new XPS 15 9500 with 10th Gen Intel and I can't get it to work with a resolution of 5120x1440 whatsoever.  Despite what @jphughan has said about the XPS 13s supporting it, I have seen a lot of issues with the 15 doing so.  I have tried connecting to the monitor with two different thunderbolt3 cables, and neither connection allows me to choose 5120x1440 at any refresh rate.  If I go to the display adapter for the Intel UHD it doesn't even list 5120x1440 as a supported mode.  I have tried multiple versions of the UHD driver with no luck.  As it stands, I'm stuck using this laptop in 3840x1080.

@jbeg  Intel had a buggy driver release a while ago that caused 5120x1440 displays to be limited to 3840x1080.  See this post I wrote about it, which includes a link to a thread about it on the Intel forums.  That was admittedly a while ago and it's not the same generation of XPS 15, but it may still account for the behavior you're seeing.

@jphughanI read multiple posts like that (including that exact one) which is why I tried different intel uhd driver versions.  They all had the same issue in that the adapter itself didn't list 5120x1440 as a supported mode nor could I do it as a custom one.  I looked to see if I could just use Nvidia as the base graphics adapter since it's a 1650Ti but there was no way to do it.  With everything I've tried I've never been able to get 5120x1440 as a supported mode.

@jbeg  In that case I'm not sure how to account for your lack of success when others are seeing confirmed success even on older systems.  You can't use the NVIDIA GPU directly unless the system has the display outputs wired to it, and on the XPS 15 9500, all outputs seem to be wired to the Intel GPU.  The XPS 17 9700 has a BIOS option allowing you to change this because it has a motherboard design that allows this type of switching, but thatt doesn't seem to be available on the XPS 15 -- and apparently even on the 17 it's only available on systems that have an RTX GPU, not a GTX GPU.

Hi everybody,

Wow, just have been reading your posts here, which are really interesting - but also too sophisticated for me to be honest, didn't understand everything yet... 

I've a XPS15 9560 and wanted to switch to 5120 x 1440 resolution for my external LC49RG90SSRXEN monitor. As I understood, my old system neither has the direct wiring of the internal GTX GPU to the used thunderbolt connection, nor it has the BIOS setting to switch to, and thus I will not get the full resolution of 5120 x 1440 externally. Is this correct?

But on the other hand I heard from people which were able to do so with the same hardware. Is it possible with a special driver using the (weaker?!) internal Intel GPU (Intel HD Graphics 630)? Thanks for some hints for a greenhorn in this area...

@Edimahler  It's true that your system's outputs are controlled by the Intel GPU, but the Intel GPU should still support 5120x1440, since that is slightly fewer total pixels than 4K (3840x2160), which that Intel GPU supports.  However, it seems that 5120x1440 has been a bit of an odd duck.  In January 2020 Intel released a driver version that inadvertently broke 5120x1440 support.  That was eventually fixed, but it seems at some point the HD 630 specifically had it disabled by default but it was possible to re-enable it with a registry tweak.  That's the reason that Dell offers this patch.  It's indicated as applying to the U4919DW, which is Dell's own 5120x1440 display, and it's categories as a firmware update, but if you open the zip file it's just a REG file that applies some settings that have nothing to do with that specific display.  And the description at the top of that page specifically says it's meant to enable 5120x1440 support on the Intel 630 GPU.  I haven't personally tested that since I don't have the necessary equipment, but it seems like 5120x1440 should still be possible, even though it seems it requires a bit more effort than it used to for whatever reason.  But I've worked with people to run 5120x1440 displays even on an old XPS 13 9350 system, which is 5 generations older than the XPS 15 9500 and of course a lower-end system than the XPS 15 in general.

Thank you VERY much for your detailed answer! Will try this next week, as soon as I'm back to office. Anyway, it's really strange, that

a) the weaker graphics chip of the two in my system is able to display with this resolution, the other not.

b) Dell breaks the support of this resolution in a newer version of the driver. What about using the older driver? Is it still available? Security risks?

For now I'll try with the registry trick and will let you know about the result here again.

Have a nice weekend and thanks so much again in advance!

@Edimahler  Happy to help, but to clarify:

1. It’s not that the other GPU (the NVIDIA GPU) doesn’t support 5120x1440. It’s that the NVIDIA GPU as implemented in the XPS 15 is not directly wired to any display outputs. It does support 5120x1440, but the Intel GPU is the key factor in this case.

2. It wasn’t Dell who issued the problem driver. Intel makes the Intel GPU driver, and updates for that driver can be delivered even through Windows Update. But things breaking in a driver update isn’t all that strange, unfortunately. As for the older driver still being available, you may be able to find it somewhere, but there have been security updates fixed in Intel Graphics drivers since late 2019.

@jphughan Thanks again for your explanations, which all make sense.

This morning I took myself some hours to try with your patch (even though it's not compatible with my system, as they say (I've the service tag 3YDVXF2)), with different Intel HD630, HD620 and Iris drivers, also the version 26.20.100.7263 given here

https://www.dell.com/community/XPS/Xps15-9560-with-Samsung-CRG9-super-ultra-wide-monitor-32-9/m-p/7495496#M49513

but I was definitely NOT successfull with all of this. Really disappointing. I always just get the 3840 x 1080 resolution as maximum.

What the heck is different in my case, compared to the user "nickynackynew" in the link above? I've also a Xps15 9560 with a Samsung screen, even though it's a Samsung C49RG94SSU instead. Does this really make the difference?

Is there maybe a limitation in the total amount of pixels displayed, because I'm using an extended desktop using my primary, internal 4K screen of the laptop together with the external Samsung screen?

Or is the culprit the dockingstation WD19, which still is in between (thunderbolt towards laptop / Displayport towards screen)? According to Dell, the dockingstation and my laptop should be able to deliver the 5120x1440... Wished I would understand it...