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jessicaroyale
1 Copper

connect XPS 15 9560 to two external monitors

I have an XPS 15 9560 laptop with thunderbolt and hdmi and usb ports.
I want to connect it to two external monitors that i have:
  1. DELL P2715Q
  2. LG 29UM68-P
​here are the specs of the monitors:
DELL P2715Q
 
 
 
rf4ef2vxkij11DELL P2715Q
 
 
LG 29UM68-P
 
 
 
zb8c5lm0lij11LG 29UM68-P
 
the spec sheet for LG says:
HDMI 2 (ver1.4)
DisplayPort Yes (ver1.2)
there is a bit of instructions on how to do MST connections, but i am not sure if i can do it with this LG and how.
DP MST connection
 
c5ck0o77lij11DP MST connection
 
and I have this multi adapter at my disposal.
 
 
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I am clueless on how to do it without any external docks or whatsoever. How is it possible to use the MST feature of the DELL monitor in this setup?
 
 
 
Any tips or ideas?

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3 Replies
Tedhohio
1 Copper

Re: connect XPS 15 9560 to two external monitors

Did you ever get this working?  I have been using an XPS9560 since mid 2017 and always with dual external monitors.  I have one plugged into the HDMI port of the laptop.  In my USB-C I have a Dell 470 adapter (https://www.dell.com/en-us/work/shop/accessories/apd/470-abqn) which is USB-C to HDMI, VGA, USB 3.0, Ethernet.  I use the HDMI for my other monitor.  I also use the USB 3.0 and the Ethernet connection.

What might be different is I am not running a 4K LCD or monitors, just FHD, and they all work, so I have extended the desktop on all three screens . . . usually.  Lately my laptop LCD has been a bit intermittent.  The externals work fine, but the laptop screen has been black most of the time.  I am not sure what's wrong because it has come to life at times, but after my screensaver runs, it stays black.  Not sure if it's a driver issue and something with Windows 10 and the screen saver.

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jphughan
5 Rhenium

Re: connect XPS 15 9560 to two external monitors

@jessicaroyale, your system can use MST, and technically that would be a cabling option for you since the Dell display supports it (the LG wouldn't need to explicitly support it if it's at the end of the chain), but the resolutions of your displays are too high to run both of them at their native resolution and refresh rates in that configuration.  The DisplayPort 1.2 signal available out of the USB-C connection simply doesn't offer enough bandwidth for that.  If you had dual 2560x1440/1600 displays, MST would be fine, but the P2715Q is a 4K 60 Hz display, which consumes an entire DisplayPort 1.2 channel all on its own.  If you enable MST on that display, it limits itself to 4K 30 Hz in order to have enough bandwidth left over to pass down the chain to something else, but 30 Hz isn't a satisfactory experience for most people, so keep MST disabled on the Dell display so that you can use 60 Hz.

In terms of how you can run both displays at their native resolutions and refresh rates simultaneously, you have a few options:

- Connect your P2715Q using a USB-C to DisplayPort cable and your LG Ultrawide via HDMI.  Connect the USB-C end of that cable directly to the system, NOT through any sort of adapter like the one you mentioned, for reasons I explain in my next reply below.

- Get a Thunderbolt 3 to Dual DisplayPort adapter and connect each display to that adapter via DisplayPort.  Fyi this adapter is NOT the same as a USB-C DisplayPort MST hub, which looks similar and costs less.  The difference is that by tapping into your system's Thunderbolt 3 capability, this type of adapter gains access to two DisplayPort 1.2 outputs, thereby offering enough bandwidth to drive both displays out of that one connector.  A USB-C DisplayPort MST hub would only tap into a single DisplayPort 1.2 channel, which won't be enough.

- Buy a TB16 dock with a 240W adapter, and connect both displays to the dock.  The P2715Q would have to use either of the DisplayPort outputs, and the LG could use either the remaining DisplayPort output or HDMI.  This setup would also allow both displays to run at their native refresh rates, and you get the added benefit of having everything coming to your system via a single cable -- including power to charge the system -- but obviously it's more expensive than the other solutions.  Note that the power to charge the system is why you'd need the TB16 specifically with the 240W adapter, not the 180W version that's also available.  The 180W version isn't able to allocate enough power to the attached laptop to run the XPS 15 models properly.

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jphughan
5 Rhenium

Re: connect XPS 15 9560 to two external monitors


@Tedhohio wrote:

Did you ever get this working?  I have been using an XPS9560 since mid 2017 and always with dual external monitors.  I have one plugged into the HDMI port of the laptop.  In my USB-C I have a Dell 470 adapter (https://www.dell.com/en-us/work/shop/accessories/apd/470-abqn) which is USB-C to HDMI, VGA, USB 3.0, Ethernet.  I use the HDMI for my other monitor.  I also use the USB 3.0 and the Ethernet connection.

What might be different is I am not running a 4K LCD or monitors, just FHD, and they all work, so I have extended the desktop on all three screens . . . usually.  Lately my laptop LCD has been a bit intermittent.  The externals work fine, but the laptop screen has been black most of the time.  I am not sure what's wrong because it has come to life at times, but after my screensaver runs, it stays black.  Not sure if it's a driver issue and something with Windows 10 and the screen saver.


@Tedhohio, the model of that adapter is actually the DA200.  The 470 you mentioned is just the first segment of its part number.  However, the DA200 is limited to 1080p output even over HDMI.  The newer DA300 can go higher, but even that would be limited to 2560x1600 on the XPS 15 9560.  It can only do 4K 60 Hz when the DA300 itself is connected to a system that outputs DisplayPort 1.3 over USB-C, which the XPS 15 9560 doesn't.  The reason video output even on the DA300 is limited relative to a direct USB-C connection (which would allow 4K 60 Hz on the XPS 15 9560) is because when you have an adapter that carries other traffic, like USB 3.0 and Ethernet (which itself runs over USB 3.0), then display bandwidth gets cut in half to allow that traffic to be passed.  I wrote a detailed post about the various operating modes of USB-C here if you're curious.

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