XPS 15, three external displays, need more thunderbolt ports

Question

Hi,

I'm planning on moving away from my Mac 2017 and the Dell XPS 15 i9 32GB RAM seems to be the best option at the moment, but I have a problem...

Currently I work on a very special setup that includes using a big 24" HDMI screen (easy there, no problem) and 2 portable external USB-C thunderbolt screens (Asus MB,169c+). It's nice as when booting to windows I can use then even for gaming (not on Mac, but on windows I can as you can see here https://www.youtube.com/watch?v=60u1Yhlb-v8)

So, it's kind of a big deal to me to keep being able to use the 2 USB-C Thuderbolt screens, as I don't want to be "downsized" on the level of productivity I've achieved with 4 screens (and also because I can carry 2 up and down everywhere I go). I've researched for adapters and seemed that the WD16 is the only good option, but this option only has a single usb-c output (as a matter of fact, every other adapter in the market seems to also play that sick joke: you can connect 10.000 USB-A stuff, but you just can't get 2 usb-c thunderbolt devices together).

What I need help with is: does anybody successfully connected 2 usb-c screens to a dell xps 15? Which adapter did you use for it? Or, does the Dell XPS 15 includes more than 2 usb-c adapters?

Please, note: I'm mentioning thunderbolt with USB-C always together, as the extra USB-C ports on the adapter needs to be capable of working with a displayport/thunderbolt on all the ports it offers.

jphughan · Accepted Answer

First, just for clarification, the MB169C+ just requires a USB-C port that has DisplayPort Alt Mode capabilities. It does not use Thunderbolt at all. Thunderbolt and display output capabilities are separate from each other.

However, the fundamental issue is that the current "regular" XPS 15 (as opposed to the XPS 15 2-in-1) only has a single USB-C output. There are things like DisplayPort MST hubs that plug into that USB-C port, which allow running multiple displays from that port, but as the name suggests, they provide DisplayPort outputs. I don't know of an equivalent that plugs into a USB-C port and gives you more USB-C ports that are all capable of DisplayPort Alt Mode. Another likely issue is that a single USB-C port probably won't provide enough power to run both of those displays and the hub itself.

The only options I can think of are less than ideal:
- Consider the XPS 15 9575 2-in-1, which has multiple USB-C ports (which also support Thunderbolt 3).
- Consider the newer ASUS MB16AC.display. My wife has it, and it can be driven via either USB-C (via DisplayPort Alt Mode) or regular USB-A (if the system has a DisplayLink driver installed).
- Wait for the next "regular" XPS 15, which will likely have more than one USB-C/TB3 port, although I don't know when it will come out.
- Look at another system. The nearest equivalent to the current XPS 15 is the Lenovo X1 Extreme, but it does have two USB-C/TB3 ports.

jphughan · Accepted Answer

@Dell XPS 15 2-in-1 wrote:

I got a USB-C to DVI adapter, but the Intel HD Graphics only allows 3 displays and doesn't recognize the built-in display (the computer display settings see all 4). I have a Dell XPS 15 9575 with Intel HD Graphics 630 and Radeon RX Vega M GL Graphics (Intel said the Radeon should allow up to 6 displays but depends on Dell). I have two external monitors connected to the Dell Thunderbolt Dock TB16 and one connected via the USB-C to DVI adapter (previously had all three external monitors connected via the dock). Do I need to get a DisplayLink adapter instead?

@Dell XPS 15 2-in-1 yes. In most laptops that have dGPUs, all of the display outputs are still wired to the Intel GPU so that the dGPU can be completely disabled when its horsepower isn't needed, thus saving battery life. On the NVIDIA side, this is called Optimus. I'm not sure what AMD's term is. But in that setup, the maximum display capabilities of the dGPU are irrelevant since it's not controlling any displays, and as of this writing there are no Intel GPUs that support more than 3 simultaneous independent displays, regardless of how they're connected or what resolution you're using. If you want to use 4 displays, at least one of them will need to be driven by an adapter or dock that uses DisplayLink technology or some equivalent indirect display technology. Note that if you go down this road and ever decide to have multiple displays connected through indirect display technology, make sure all adapters/docks use the same indirect display technology. I've seen notes on DispayLink adapters that they won't work if some other similar driver is installed, and notes on other equivalent but non-DisplayLink adapters that they won't work if DisplayLink is installed. Just be aware that indirect display technology has its share of drawbacks, which I discussed in this thread, specifically the post marked as the answer.

jphughan · Answer

@Phacjkwer, I just thought of one other thing you'll probably want to know. The XPS 15 9570 will only support up to 3 simultaneous independent displays at a time, including the built-in display if it's active, because currently there aren't any Intel GPUs that support more than that. In MOST systems that have multiple GPUs, all display outputs are still wired to the Intel GPU, and the discrete GPU when active operates as a render-only device that passes completed frames to the Intel GPU for output to the displays. The main reason for this design is battery life, because in systems that have the discrete GPU wired to display outputs, the discrete GPU has to be active whenever a display is attached to one of those outputs, even if nothing graphics-intensive is going on. The MacBook Pro has its discrete GPU wired to its outputs, which is why it can run more than 3 displays. The Lenovo X1 Extreme also seems to have its discrete GPU wired to its USB-C/TB3 outputs (and maybe the HDMI output?), which is why it too claims support for more than 3 displays.

The only other way to work around this limitation is to use DisplayLink-based displays that would normally attach via USB-A, because those displays aren't driven directly by the GPU, so they don't count towards your total. DisplayLink can support up to 10 displays just over DisplayLink, in addition to whatever is being driven by your GPU. However, the fact that DisplayLink displays aren't driven natively by the GPU introduces its own set of drawbacks. One of them is that due to a Windows limitation, DisplayLink displays when used on systems with multiple GPUs can only be accelerated by the primary GPU, and that will always be the Intel GPU when one is active. So basically, nothing being shown on a DisplayLink display will ever benefit from the NVIDIA GPU's horsepower, just in case you ever need to display anything graphics-intensive on those displays.

Phacjkwer · Answer

But this model has a GTX 1050 Ti MaxQ too. :-) On the macbook (which also has an intel and a radeon graphics cards) I could run all the 4 screens with no problems using the Radeon. Also, my not does not has a 4K screen, I've ordered with the full hd as i would require less from the video card leaving it free to be able to run more screens. I will order an adapter from Amazon today to split 2 screens on the USB-C to Display Port adapters and tell you later if it worked.

jphughan · Answer

@Phacjkwer wrote:But this model has a GTX 1050 Ti MaxQ too. :-) On the macbook (which also has an intel and a radeon graphics cards) I could run all the 4 screens with no problems using the Radeon. Also, my not does not has a 4K screen, I've ordered with the full hd as i would require less from the video card leaving it free to be able to run more screens. I will order an adapter from Amazon today to split 2 screens on the USB-C to Display Port adapters and tell you later if it worked. Yes I realize that you have a GTX as well, but unless the GTX is physically wired to any of the display outputs as is the case in the MacBook having GTX won't change anything in terms of maximum allowed displays.  In most laptops with multiple GPUs, only the Intel GPU is actually wired directly to any of the outputs, so you're still subject to all of its limitations, including maximum simultaneous independent displays.  The discrete GPU just acts as a 'render-only' device as needed, which means you wouldn't be able to split your displays across both GPUs.  I already explained that in my second post above.  The internal display resolution doesn't make a difference here either.  Today's Intel GPUs only support up to 3 simultaneous independent displays, regardless of resolution.  There are also potential bandwidth issues that might affect how you can connect them, and those limitations would be affected by resolution, but the 3 display max exists no matter what.That said, I've read posts suggesting that on the 9570, the HDMI output might be wired directly to the NVIDIA GPU, and since it's HDMI 2.0, it would 4K 60 Hz if your display also had an HDMI 2.0 input.  If you want to verify wiring, check NVIDIA Control Panel.  The multi-display section indicates which outputs are wired to which GPU.  If the HDMI output is in fact wired to the NVIDIA GPU, you may be able to connect one of your displays that way to get four total.  The previous XPS 15 models (9560, 9550, and 9530) had all outputs wired to the Intel GPU, so there was no way to use more than 3 total independent displays.

Phacjkwer · Answer

&#xa0;I was able to add 3 screens. As you said, I had to add a Display link screen. That's ok, I use it for choosi anyway. This setup worked fine on Linux.&#xa0;&#xa0;

Dell XPS 15 2-in-1 · Answer

What USB C to DisplayPort Adapter did you buy?

jphughan · Answer

@Dell XPS 15 2-in-1 wrote:

What USB C to DisplayPort Adapter did you buy?

@Dell XPS 15 2-in-1you don't have to worry about specific adapters beyond making sure you don't buy from a brand that makes unreliable junk in general. The reason is that all USB-C ports with video output capabilities have to support at least DisplayPort 1.2, which means any adapter/cable will support that spec. And the XPS 15 models don't support newer DisplayPort standards over USB-C because Intel GPUs still don't support the newer versions. That support won't be arriving until the Ice Lake CPU family arrives with the new Gen 11 integrated GPU. So again, that means that any USB-C to DisplayPort adapter or cable from a reliable vendor will work fine and will allow the system to use its full capabilities. I happen to have this one and it works great.

Dell XPS 15 2-in-1 · Answer

I got a USB-C to DVI adapter, but the Intel HD Graphics only allows 3 displays and doesn't recognize the built-in display (the computer display settings see all 4). I have a Dell XPS 15 9575 with Intel HD Graphics 630 and Radeon RX Vega M GL Graphics (Intel said the Radeon should allow up to 6 displays but depends on Dell). I have two external monitors connected to the Dell Thunderbolt Dock TB16 and one connected via the USB-C to DVI adapter (previously had all three external monitors connected via the dock). Do I need to get a DisplayLink adapter instead?

Ticked11 · Answer

When I decided to upgrade my laptop i knew i wanted minimum 3 displays possibly 4. I am not a techie just a plug n play avg joe. I looked that the dell xps 15 n precision workstation. I saw they didn't enough display ports n thought well maybe they r trying to make people buy a dell type c dock to add more monitors. I hate carrying adapters or docks because some can be unstable.

ALMOST EVERY gaming brand came with the requisite display ports (3 -- hdmi, mini display, type C display port). Never really thought about the intel limitations highlighted by the posters BUT why should I -- Why put in 3 display ports n not be able to connect 3 external monitors for 4 display setup. Well I bought the MSI GS65 Stealth. Yep first try, VOILA 4 displays (3 externals via hdmi w USB A power, mini display w USB A power, type c video n power). Plug n play.

Why Dell didn't design this into their laptops (ex Alienware) is a major mistake? Solution buy any gaming laptop (every other brand have 3 display ports) n sell Dell XPS on EBAY.

XPS

XPS 15, three external displays, need more thunderbolt ports

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