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Dell XPS 13 9300 Dual 4k

I recently purchased a Dell XPS 13 9300 (2020) Developer Edition and I have 2 external 4k monitors (Dell U2718Q).I bought this hub on Amazon: https://www.amazon.com/gp/product/B07X5KSBNJ/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1. It has two HDMI ports, and from my understanding a thunderbolt 3 display signal can be split into two connections with an adapter like this. Unfortunately it only seems to support both monitors if I set the resolution to 1080p. Using just one works fine. Are dual-4k monitors possible? From my research it seems like it should be. Could this perhaps be a driver issue since I'm using Ubuntu Linux with the developer edition? I haven't touched the drivers, and I assumed this would work out-of-the-box. Do I need to use two separate cables? Does anyone have any cable setup that they know works? Thanks!

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@zachary592  The post above is correct.  The hub you have only taps into USB-C, which only gives you access to at most a single DisplayPort interface from the system.  Since the XPS 13 9300 supports DisplayPort 1.4, then with the right hardware, that could be enough to run dual 4K 60 Hz, but the problem is that a hub like that would be setting up the USB-C link to support carrying video and USB 3.x data simultaneously.  Carrying USB 3.x requires two of the four high speed lanes available in a USB-C link, so carrying it cuts your display bandwidth in half compared to what you'd have with something like a DisplayPort MST hub or a USB-C to DisplayPort cable, either of which would allocate all four lanes in the USB-C link to video.  But if your current hub only supports DisplayPort 1.2, and therefore you only have half of a DP 1.2 interface to work with, that's only enough bandwidth for dual 1080p displays or a single 4K 30 Hz display.

If you want dual 4K 60 Hz displays and USB 3.x data, you'd need a Thunderbolt dock.  A DisplayPort MST hub that supported DisplayPort 1.4/HBR3 would allow dual 4K 60 Hz -- but without USB 3.x data.  A Thunderbolt 3 to Dual DisplayPort (or Dual HDMI 2.0) adapter would also work, even if the latter only supported DisplayPort 1.2/HBR2.  The reason is that Thunderbolt 3 can tap into two independent DisplayPort interfaces, and dual 4K 60 Hz can be run either from a single DisplayPort 1.4 interface or two DisplayPort 1.2 interfaces.  But the small TB3 to Dual DP/HDMI 2.0 adapters also typically only support video outputs.

So like I said, what you really need is a dock like the Dell WD19TB.  Note that when running dual 4K 60 Hz displays with that dock, there are some restrictions about the combination of ports you can use.  They're spelled out in the manual available on support.dell.com.  The XPS 13 9300 is a Thunderbolt-capable DisplayPort HBR3 system, just to make sure you look at the right section of the Display Resolution Table.  The WD19TB is obviously quite a bit more expensive, but keep in mind that it at least comes with a power adapter, which will free up your existing power adapter to be used somewhere else, e.g. parked somewhere else in your home where you spend a lot of time or kept in your bag so you don't have to get it out and pack it up every time you want to use your laptop with your displays.

If you're curious, I did an explainer post on the various operating modes of USB-C and TB3, with particular focus on the impact to possible display setups, over here.


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The adapter you linked to seems to support dual 4K only at a maximum of 30Hz (as seen in their description). This is probably because they are simply splitting a single DisplayPort 1.2 signal into two. Have you tried changing your monitor settings to 4K with 30Hz refresh rate to see if it works?

To output to dual 4K monitors at 60Hz, you need either a USB-C to DisplayPort 1.4 adapter with MST support, or a Thunderbolt 3 to dual DisplayPort adapter (which works on laptops such as the XPS 9300 which support two DisplayPort outputs from one port).

So far, this Thunderbolt 3 adapter seems to work fine for me with a 4K TV at 60Hz (via a HDMI-DP adapter) and a separate 1440p monitor at 144Hz (which i understand has similar bandwidth requirements to 4K at 60Hz): https://www.amazon.com/gp/product/B075T6BBQD/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1

There is also this adapter which can support up to 3 4K monitors and Power Delivery passthrough. However, at present, there seems to be some compatibility issues with this adapter after the latest BIOS update so I would not recommend it yet.

Great thanks for the reply! Do you also own the developer edition? My worry is that the adapter I used seems like it should have worked, just maybe not at 60hz like the one you linked. I'm worried that perhaps it's a driver issue with the developer edition and it might not be possible.

@zachary592  The post above is correct.  The hub you have only taps into USB-C, which only gives you access to at most a single DisplayPort interface from the system.  Since the XPS 13 9300 supports DisplayPort 1.4, then with the right hardware, that could be enough to run dual 4K 60 Hz, but the problem is that a hub like that would be setting up the USB-C link to support carrying video and USB 3.x data simultaneously.  Carrying USB 3.x requires two of the four high speed lanes available in a USB-C link, so carrying it cuts your display bandwidth in half compared to what you'd have with something like a DisplayPort MST hub or a USB-C to DisplayPort cable, either of which would allocate all four lanes in the USB-C link to video.  But if your current hub only supports DisplayPort 1.2, and therefore you only have half of a DP 1.2 interface to work with, that's only enough bandwidth for dual 1080p displays or a single 4K 30 Hz display.

If you want dual 4K 60 Hz displays and USB 3.x data, you'd need a Thunderbolt dock.  A DisplayPort MST hub that supported DisplayPort 1.4/HBR3 would allow dual 4K 60 Hz -- but without USB 3.x data.  A Thunderbolt 3 to Dual DisplayPort (or Dual HDMI 2.0) adapter would also work, even if the latter only supported DisplayPort 1.2/HBR2.  The reason is that Thunderbolt 3 can tap into two independent DisplayPort interfaces, and dual 4K 60 Hz can be run either from a single DisplayPort 1.4 interface or two DisplayPort 1.2 interfaces.  But the small TB3 to Dual DP/HDMI 2.0 adapters also typically only support video outputs.

So like I said, what you really need is a dock like the Dell WD19TB.  Note that when running dual 4K 60 Hz displays with that dock, there are some restrictions about the combination of ports you can use.  They're spelled out in the manual available on support.dell.com.  The XPS 13 9300 is a Thunderbolt-capable DisplayPort HBR3 system, just to make sure you look at the right section of the Display Resolution Table.  The WD19TB is obviously quite a bit more expensive, but keep in mind that it at least comes with a power adapter, which will free up your existing power adapter to be used somewhere else, e.g. parked somewhere else in your home where you spend a lot of time or kept in your bag so you don't have to get it out and pack it up every time you want to use your laptop with your displays.

If you're curious, I did an explainer post on the various operating modes of USB-C and TB3, with particular focus on the impact to possible display setups, over here.


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Wow thanks so much for the response! That answers a lot of questions I had.

I am reading this thread with interest.  I have an XPS 13 9300 i5-1035G1 (2020) purchased in March, and it has been just fine in stand alone.  I am now preparing to stress it to the capabilities for which it was purchased.

Portable and light for travel is perfect.  My home office / man cave will put the machine to the test.  I use dual large screen (55") 4k UHD HDR wall mounted TV monitors.  Cable length involved demands HDMI.  I am unwilling to compromise performance for length, so I will use the only the best HDMI fiber cables.  

https://www.amazon.com/gp/product/B07LD6MBNL/ref=ox_sc_act_title_2?smid=A1PQTFLDAVXKKK&psc=1

Next, I need a little extra Thunderbolt 3 cable length between the laptop and a Thunderbolt 3 docking port, hub, or whatever.  I looked at every 6.5ft active cable I could find, but none of the reviews cut the mustard.  That length is apparently questionable for Thunderbolt 3.  I looked for a fiber optic version - ha!, waste of time.  So, I settled on this as the best cable for my needs.

https://www.amazon.com/gp/product/B08C4M6BVZ/ref=ox_sc_act_title_3?smid=A1WU736W1PHVH9&psc=1

Now, I must find a compatible Thunderbolt 3 docking port / hub / adapter combo to make the whole thing work.  I could go with a dock that has DP1.4 ports.  Thunderbolt 3 docks with dual HDMI ports seem relatively rare.  I am considering using multiple active DP1.4 to HDMI adapters for the displays, but the engineer in me favors minimizing potential points of failure.  Many of the docks also have a Thunderbolt 3 pass-thru port.  Maybe that's the way to go for the displays.  I will also need USB ports for an external drive, thumb drive, wireless mouse, and cell phone.

Theoretically I should be able to get laptop charging and all communications over a single Thunderbolt 3 port and cable with the right setup.  If I must use both Thunderbolt 3 ports, I will.  What about using the downstream port for display only?  The HDMI fiber optic cables require insignificant power.  The upstream port could be for laptop power and other other peripherals?  This all assumes no issues with the laptop itself and no issues between the chair and keyboard.

Any recommendations on my setup would be welcome.  I am a little concerned given the problems others have experienced with Thunderbolt 3 on this laptop.  I am looking for whatever setup will be the most reliable.  That's the main point.

 

 

@AnimalMagnet  I'm not sure, but I don't think you can run dual 4K 60 Hz with HDR from a TB3 dock, at least not if you want to use full chroma, but I'm not even sure the Intel Graphics drivers allow you to use chroma subsampling.  And according to a few other threads around here, people seem to be having trouble even getting dual 4K 60 Hz SDR working through the WD19TB.  Unclear at this stage whether that's an issue specific to the XPS 13 9300 with the WD19TB or the XPS 13 9300 in general, although given the number of other complaints about Thunderbolt 3 and even USB-C display issues with the XPS 13 9300 at the moment, I wouldn't be surprised if it was the latter.

For your HDMI cables, there are all sorts of passive 25-foot cables rated for HDMI 2.0b that cost a lot less.  They'll be thicker than fiber-based cables if that's an issue for you, but other than that, you're not going to gain more performance by spending more money.  If the passive cables work and don't incur dropouts, then that's as good as it's going to get.  You're dealing with a digital signal here.  Budget isn't a constraint for me either when I'm dealing with tech things, but that still doesn't mean I'd rush to spend $100 on a cable without first seeing if a cable that costs a small fraction of that amount would deliver the same end result.

For your active TB3 cable, I can't say I've ever heard of the cable brand you've found.  If I had to get an active Thunderbolt 3 cable, it would probably be from either Cable Matters or StarTech, both of whom have solid reputations for making quality products, which is why I buy several products from both brands.  I don't put a ton of stock into Amazon reviews especially when it comes to techy products, since a bunch of times people writing bad reviews were trying to use it in a way it specifically was not meant to be used and/or got tripped up by an interoperability issue between the product they were reviewing and whatever other product they were trying to use it with.

I suspect TB3 docks with dual HDMI outputs are relatively rare because DisplayPort is simply a superior output, which has been the case ever since it was released when compared against the HDMI standard of the time.  Compared to HDMI 2.0, DisplayPort 1.4 can handle more bandwidth, supports DisplayPort MST, and can offer Dual Mode DisplayPort to allow even passive DP to HDMI adapters -- and unlike HDMI that requires the manufacturer to pay a royalty for every HDMI port or connector they put onto a product, DisplayPort is royalty-free.  I'm right there with you in terms of keeping things as simple as possible, which is why I try to avoid active adapters if the situation allows, but unfortunately if you're trying to run 4K 60 Hz HDR, that's probably your only option.  Technically there is a Dual Mode DisplayPort standard that allows a DisplayPort output to send HDMI 2.0 signalling natively, but I haven't seen any passive DP to HDMI adapters support that level of the standard, and of course you'd need the dock output to support it as well.  But then you still have two other potential problems:

  • Although DP 1.4 can support 4K 60 Hz HDR with full chroma, HDMI 2.0 can't, which means the only way you'll get that signal to the HDMI 2.0-based TV is by running reduced chroma.  But I'm not sure the Intel GPU in that system supports it.
  • Even if it does, as mentioned above, I'm not sure TB3 itself offers enough bandwidth to run two such connections.  If DisplayPort DSC were available between the system and dock, then it would be no problem at all, but it's unclear right now whether the Intel GPU in that system supports DisplayPort DSC, and then you'd also need a dock that could accept a DSC signal from the system, and then the dock would either need to decompress it internally or you'd need to find active adapters that could do that.

I'm not sure what you expect the "downstream" Thunderbolt port on the dock to get you in terms of your displays.  You can use it as a USB-C video output, or if you had an actual native Thunderbolt display, you could use it for that.  Otherwise, it's there for actual TB3 peripherals, such as fast SSDs or storage arrays, external GPUs, etc.

However, using a dock for ONE of the displays and other connectivity such as power and USB, and then connecting the other display directly to another USB-C/TB3 port on the system may well be worth considering, since in that case you're no longer trying to satisfy both displays' bandwidth requirements over TB3.  This adapter specifically supports DisplayPort 1.4 input from USB-C and HDMI 2.0b on the output.  And incidentally if you were to get the WD19TB dock, you could use this on either its USB-C video output or its "downstream" TB3 port.


Totally rethinking my needs.

You are correct about the graphics, but it occurred to me that I don’t need the full-on 4K 60Hz UHD HDR that the monitors can handle.  Not even half that.  I trade in stock options, and the graphics are fairly static.  I watch charts of prices and indicators on a real time basis, looking for clues and trends for entry and exit points.  Still, it’s only a chart.  It might be complex to the untrained eye, but the graphics certainly don’t move very fast – even when things are “volatile”.  It does not need to be high definition, high refresh rate video.  I could easily get by with 4k 30Hz and probably much less.  The Intel UHD Graphics card will easily do the job (presuming I can get everything else to work as it should).  I do not plan on projecting movies or videos from the laptop.  I use other sources and short distances for that purpose.

The WD19TB was on my wish list, but it has a fixed length TB3 cable that is too short.  This is a non-negotiable requirement, so I will need something else.

This also brings the HDMI cables back into focus.  Cable thickness is a non-issue.  A good copper HDMI cable should do the job.  And the whole active / passive issue - it did cross my mind that active vice native is another potential failure point. 

This has been very helpful.  Back to the drawing board.  My biggest concern remains not knowing what WILL work reliably with the XPS 13 9300.  I hope this will resolve over time.

@AnimalMagnet  Ok, your use case definitely doesn't require HDR, so that simplifies things quite a bit.  But even though you don't need 60 Hz, the XPS 13 9300 at least SHOULD be able to support dual 4K 60 Hz through TB3, although problems have been reported achieving this through the WD19TB.  There are other TB3 docks like the CalDigit TS3+ or USB-C Pro Dock (the latter of which despite the name will use Thunderbolt capabilities if available from the source system), both of which support dual 4K 60 Hz.  They might perform better with the XPS 13 9300 in this regard, but I haven't seen reports one way or the other.  The WD19TB is certainly confirmed to work with dual 4K 60 Hz displays overall (i.e. with other systems), but it's unclear whether the issues with the XPS 13 9300 are something purely on the system side or some weird interoperability issue with the specific combination of that system and the WD19TB.

But if you don't care about HDR, then if I were planning your setup, I would this if I had to use a DisplayPort output from whatever dock I was running.  Plugable has a solid reputation for producing quality stuff, and I've recommended that adapter for people who wanted to use DisplayPort daisy chaining with an HDMI-only display at the end.  That wouldn't normally be possible, but an active adapter like that makes it possible.  And if I had a dock where they only OTHER display output was a USB-C or downstream TB3 port, then I'd get an active USB-C to HDMI 2.0 adapter.  On that subject, I've seen multiple cases now of people reporting those dongles not working with particular laptops even though they work with other devices, and in those cases they got a different brand of dongle that turned out to work with both systems.  So to your point about keeping things simple where possible, it seems active adapters don't always work where they should.  But unless you find a dock that has a native HDMI 2.0 output, an active adapter of some kind is going to be your only option.

But yes, unfortunately it seems like the biggest obstacle here may be the XPS 13 9300 itself, at least in its current firmware/driver state.  But if you're feeling adventurous, check out those CalDigit dock models I mentioned.  Neither one of them uses a permanently attached cable.  But be aware that they're both also limited to DisplayPort 1.2.  That's fine for dual 4K 60 Hz, but it's still a bit old today.  There's also the Lenovo Thunderbolt 3 Dock Gen 2 (model 40AN), which I have.  It supports DisplayPort 1.4 and is pretty similar to the WD19TB overall, except it doesn't have a permanently attached cable either.


@AnimalMagnet  Having thought about this overnight, if it makes you feel any better about the prospect of using active adapters, consider that an active conversion somewhere in the chain is your only option with this system anyway.  Even if you did find a dock that had an HDMI 2.0 output built in, the dock would essentially have an integrated DisplayPort to HDMI active converter.  The reason is that the system's USB-C/TB3 ports will only output DisplayPort.  In fact, some laptops that have built-in HDMI 2.0 outputs use an internal active DP to HDMI converter because they have GPUs that don't natively support HDMI 2.0, so they essentially grab a DisplayPort 1.2 interface off the GPU and run it through a converter before exposing it as an HDMI 2.0 port on the chassis.

If you want dual native HDMI 2.0, you'd probably be looking at a desktop GPU, either in a desktop system or installed into an external GPU enclosure that you'd connect to your laptop, although the latter would be a pretty big waste of resources in your case.  And even the desktop GPUs I've seen only seem to offer at most one HDMI 2.0 output, with the rest of the bracket space used for DisplayPort or USB-C outputs, since again they're superior interfaces.

At least with external active adapters, you have control over the adapters you choose.

(Note: There is technically a USB-C HDMI Alt Mode standard that allows a USB-C port to send a native HDMI signal, but I'm not aware of it being implemented anywhere.  Video output over USB-C is nearly or maybe even literally always over DisplayPort Alt Mode, with USB-C to HDMI adapters incorporating a converter chip.  But even if HDMI Alt Mode was implemented somewhere, any vendor that actually decided to offer a passive USB-C to HDMI adapter that relied on the source supporting that standard would almost certainly find themselves incurring a lot of product returns and negative reviews from people who simply assumed, incorrectly, that it would work with their USB-C systems that only supported DisplayPort Alt Mode -- like the wide range of existing USB-C to HDMI adapters that incorporate an active converter chip would have.  Not a great position for a product vendor to be in.  So even if HDMI Alt Mode was implemented somewhere, actually using it would be another matter.  And when using the USB-C port for Thunderbolt 3, that isn't allowed.  TB3 only supports DisplayPort for video.)


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