DG1983
2 Bronze

Does the 7501's TB3 port support multiple DP streams?

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I recently purchased an Inspiron 7501, which i believe has TB3 as part of the USB-C port.

I plan on buying a hub to connect my peripherals, and two monitors. However, i've read that some TB3 ports only support one displayport stream. Does anyone know if the 7501 TB3 port supports two streams? I guess the alternative is to use the USB-C port for one monitor and the HDMI port for the other.

Also, if the TB3 port is limited to one displayport stream, am i right in assuming that means i cant daisy-chain multiple monitors using a USB-C hub monitor?

Many thanks

 

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jphughan
7 Gold

Re: Does the 7501's TB3 port support multiple DP streams?

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@DG1983  To the best of my knowledge, every Dell model that has a Thunderbolt 3 interface has two DP outputs wired to it.  Although it's true that TB3 allows the option of only having a single DP interface, I don't think Dell has ever used that design.  But in terms of your daisy chain question, you're not quite right, for a few reasons:

  • DisplayPort daisy chaining (DisplayPort MST) is explicitly designed to allow multiple displays to be driven from a single DisplayPort interface.  You don't need Thunderbolt for that at all.  However, the total bandwidth requirements of the daisy chain needs to fit within what's available on that single interface.
  • If you're using a USB-C display, then it's not using Thunderbolt at all, in which case you'll only have regular USB-C DisplayPort Alt Mode, which only uses a single interface.  You need to be using actual Thunderbolt 3 for dual interfaces.  And if you use a USB-C display that sets up the USB-C link to run video plus USB 3.x, then you'll only have half of a DisplayPort interface of bandwidth due to how USB-C works.  If you use a USB-C display that sets up the link for video and USB 2.0, then you'll have a full interface of bandwidth available.  More info here.
  • If you use a USB-C hub that has video outputs, this again would not be a Thunderbolt device and therefore would only tap into a single interface.  And those hubs practically always set up the USB-C link for USB 3.0 to support other functions built into the hub, which cuts you down to half of an interface.  And lastly, most such hubs do not support DisplayPort MST in order to run multiple independent displays through the hub, so even if you were going to run a display setup that would work from a half bandwidth link (like dual 1080p), the hub might not allow it.

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jphughan
7 Gold

Re: Does the 7501's TB3 port support multiple DP streams?

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@DG1983  Yes, the CalDigit USB-C Pro Dock supports TB3 if the attached system offers it, and yes you'd be able to run two independent displays.  On a Windows system, you'd be able to do that even if your TB3 interface only had a single DisplayPort interface wired to it because you'd be able to use MST (macOS still doesn't support MST), although your display setups would be more limited in that case due to the reduced bandwidth.  But with a TB3 interface that has two DisplayPort interfaces, you'd be able to run dual displays up to 4K 60 Hz each.  This is explained on CalDigit's product page for that dock. 🙂

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jphughan
7 Gold

Re: Does the 7501's TB3 port support multiple DP streams?

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@DG1983  To the best of my knowledge, every Dell model that has a Thunderbolt 3 interface has two DP outputs wired to it.  Although it's true that TB3 allows the option of only having a single DP interface, I don't think Dell has ever used that design.  But in terms of your daisy chain question, you're not quite right, for a few reasons:

  • DisplayPort daisy chaining (DisplayPort MST) is explicitly designed to allow multiple displays to be driven from a single DisplayPort interface.  You don't need Thunderbolt for that at all.  However, the total bandwidth requirements of the daisy chain needs to fit within what's available on that single interface.
  • If you're using a USB-C display, then it's not using Thunderbolt at all, in which case you'll only have regular USB-C DisplayPort Alt Mode, which only uses a single interface.  You need to be using actual Thunderbolt 3 for dual interfaces.  And if you use a USB-C display that sets up the USB-C link to run video plus USB 3.x, then you'll only have half of a DisplayPort interface of bandwidth due to how USB-C works.  If you use a USB-C display that sets up the link for video and USB 2.0, then you'll have a full interface of bandwidth available.  More info here.
  • If you use a USB-C hub that has video outputs, this again would not be a Thunderbolt device and therefore would only tap into a single interface.  And those hubs practically always set up the USB-C link for USB 3.0 to support other functions built into the hub, which cuts you down to half of an interface.  And lastly, most such hubs do not support DisplayPort MST in order to run multiple independent displays through the hub, so even if you were going to run a display setup that would work from a half bandwidth link (like dual 1080p), the hub might not allow it.

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DG1983
2 Bronze

Re: Does the 7501's TB3 port support multiple DP streams?

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Thanks very much.

So can i clarify, if I were to just connect the USB-C/TB3 port to say a Caldigit USB-C Pro hub (which i think also has TB3), then connect to two separate monitors using the displayports in the hub, i would be able to use as two independent external monitors?

Thanks again!

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jphughan
7 Gold

Re: Does the 7501's TB3 port support multiple DP streams?

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@DG1983  Yes, the CalDigit USB-C Pro Dock supports TB3 if the attached system offers it, and yes you'd be able to run two independent displays.  On a Windows system, you'd be able to do that even if your TB3 interface only had a single DisplayPort interface wired to it because you'd be able to use MST (macOS still doesn't support MST), although your display setups would be more limited in that case due to the reduced bandwidth.  But with a TB3 interface that has two DisplayPort interfaces, you'd be able to run dual displays up to 4K 60 Hz each.  This is explained on CalDigit's product page for that dock. 🙂

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DG1983
2 Bronze

Re: Does the 7501's TB3 port support multiple DP streams?

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Fantastic. Thank you very much for the help!

 

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