mockgeek
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Inspiron 13-7378, HDMI dual monitor, USB Type-C hub

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I have an Inspiron 7378 and have purchased a small hub allowing me to power my laptop as well as use a 4k monitor. I decided to make use of a second monitor (1080p only) and bought another small hub with dual HDMI ports. This second hub will drive the two monitors, but it will only do so at 1080p.

I have been reading that the TB16 handles dual monitor, but it seems that there is only one HDMI port for it. Does Dell make a hub which handles dual HDMI output with one being 4k? Or do I need to use the TB16's Display Port to handle 4k when two monitors are in play?

 

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jphughan
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Re: Regarding: HDMI Dual Monitor USB-C Hub

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@mockgeek wrote:

So, you are really saying that the USB-C port would really need to be isolated to video output (and maybe power) but not for handling the traffic associated with other USB devices at the same time?

Would the TB16 work for me if I wanted to use Display Port for the 4k and HDMI for the 1080p? Or does the lack of Thunderbolt support of the 7378 disqualify that hub? Or are you saying that the Thunderbolt option on that hub would not be something I could use?

As for the 30 Hz vs. 60 Hz, I have been using this 4k at 30 Hz long enough to not be concerned with any jitters with motion. I use this laptop for work. Outside the occasional YouTube video, I am mostly in terminal windows most of the day along with browsers on mainly static pages. I mean, I wouldn't ignore the 60 Hz option if it was available, but I can live without it.


As I described in the thread I linked, if you have a device that attempts to carry both display data and USB 3.x data, your display bandwidth gets cut in half.  Power is carried over separate pins, and in fact USB 2.0 is also carried over separate pins from the high speed lane pins that can get used for display traffic or USB 3.x, so you could theoretically run power and USB 2.0 and still have maximum video bandwidth, but typically adapters like the ones you have want to run traffic on USB 3.x because USB 2.0 would become a bottleneck for things like Gigabit Ethernet.

You can't use any devices that require Thunderbolt 3 if your system doesn't actually support Thunderbolt 3.  From what I'm seeing, your system doesn't have Thunderbolt 3, so those options are out.  Intel recently released a newer Thunderbolt controller meant to be incorporated into peripherals that would allow such peripherals to be backward compatible with regular USB-C, but I don't know if that's been incorporated into any actual products yet, and in any case the backward compatibility would come with reduced functionality, so it wouldn't solve your problem even if the TB16 had that controller.  But the TB16 doesn't have that controller; it requires Thunderbolt 3 support from the system, otherwise it doesn't work at all.

If you want to run a 4K 30 Hz display and something else, your best bet is probably the Dell D6000 dock.  It's normally not ideal for the reasons I described in the thread I linked in my second reply in this thread, but if you're ok with a 30 Hz refresh rate, you might also be ok with (or not even notice) the limitations of DisplayLink technology.  The D6000 can support up to 3 simultaneous displays all running 4K 60 Hz, and it offers USB ports, Ethernet, and charging.  The only potential catch is that the DisplayLink technology it uses requires drivers, and the only Linux distro I see drivers available for on DisplayLink.com is Ubuntu.  If you're running that, fantastic.  If not, then I'd do some digging as to whether DisplayLink is somehow available on the distro you're using.

The other option would be a USB-C DisplayPort MST hub like this one, which would dedicate your entire USB-C interface to video and therefore allow enough bandwidth to run a 4K 30 Hz display and a 1080p display simultaneously, and natively from the GPU rather than via DisplayLink.  (Note: Those MST hubs are available with either DisplayPort or HDMI outputs.  If your display setup means you need one of each, then buy the DisplayPort version and then get an active DisplayPort to HDMI adapter.  The cheaper and more common passive adapters and simple DisplayPort to HDMI cables don't always work with MST hubs and similar devices.)

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jphughan
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Re: HDMI Dual Monitor USB-C Hub

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The TB16 also has DisplayPort and Mini-DisplayPort, and there are adapters to convert both of those to HDMI 2.0, which would be enough bandwidth to handle 4K 60 Hz.  But not all DP/Mini-DP to HDMI adapters specifically support HDMI 2.0, so if you go this route, make sure you get an appropriate adapter.  But the TB16 can handle dual displays up to 4K and even some triple display setups.  The manual available on support.dell.com goes into more detail about this.  To my knowledge, Dell does not make any dock/adapter that has dual HDMI 2.0 outputs.  Part of the reason is probably that DisplayPort is a more "valuable" output, for a few reasons:

- More 4K displays on the market have a DisplayPort input than an HDMI 2.0 input because DisplayPort supported 4K several years before HDMI did
- DisplayPort supports MST which HDMI doesn't.
- It's possible to take a DisplayPort output and convert it to HDMI, but you can't take an HDMI output and convert it to DisplayPort, so DisplayPort is more flexible.

Or if you don't want an entire dock, you could get a Thunderbolt 3 to dual HDMI 2.0 adapter like this one, which can handle dual displays up to 4K simultaneously.  It looks a bit like USB-C to dual HDMI adapters, but since it taps into Thunderbolt 3, it gets access to twice as much bandwidth as a USB-C adapter, and 4x as much bandwidth as a USB-C dock like the WD15.  I wrote a detailed post about the various operating modes of USB-C and TB3 and their impact on possible display setups here if you're interested.  The catch is that the Thunderbolt 3 adapter I just linked doesn't support charging passthrough, but I haven't seen any that do.

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jphughan
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Re: HDMI Dual Monitor USB-C Hub

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Hold on a second.  According to some reviews I found, the Inspiron 7378 does not support Thunderbolt 3.  If that's the case, you would not be able to use the TB16 or the Thunderbolt 3 adapter I just mentioned.  If that system has just a regular USB-C port, the most you can get out of it is a single 4K 60 Hz display or dual 2560x1600 displays.  And even those limits assume you're using the USB-C high speed lanes solely for video.  If you're using a dock or other type of multi-purpose adapter, then your video bandwidth would be limited to a single 2560x1600 display or dual 1080p -- see the post I wrote that I linked above.  The only way to use higher-end display setups would be to use a DisplayLink adapter or DisplayLink dock like the Dell D6000, but that has some significant drawbacks that I wrote about in this thread (the post marked as the solution), so consider carefully whether you really want to go that route.

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mockgeek
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Regarding: HDMI Dual Monitor USB-C Hub

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The current hub I am using is this one:

AUKEY USB C Hub Adapter with 4K HDMI, 4 USB 3.0 Ports, 60W Type C Power Delivery Charging Port for M...

It is driving the 4k display right now at 29.98 Hz:

$ xrandr -q
Screen 0: minimum 320 x 200, current 3840 x 2160, maximum 8192 x 8192
XWAYLAND4 connected 3840x2160+0+0 (normal left inverted right x axis y axis) 600mm x 340mm
3840x2160 29.98*+

What I was trying to do this morning was to use this hub:

USB C Hub USB C Adapter Dual HDMI 4K Display, USB C to USB 3.0 2 Ports,Gigabit Ethernet , SD/ MicroS...

Which handles dual HDMI monitors but only at 1080p (59.96 Hz each). When I try to configure my display for one 4k and one 1080p, the latter actually renders but the former is just a black screen. The 4k is running at the 29.98 Hz and the 1080p at 59.96 Hz.

 

 

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jphughan
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Re: Regarding: HDMI Dual Monitor USB-C Hub

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Ok, well if you're willing to accept 4K resolution at only 30 Hz, that does open up more options in terms of display setups, but although 24-30 Hz is fine for movies, most people consider 30 Hz unacceptable for productivity work because even the mouse cursor becomes noticeably choppy.  60 Hz is the standard for PC displays.

However, both of adapters you're using are essentially "mini-docks" that are trying to use the USB-C output for both video and USB data simultaneously.  In that setup, you only have the bandwidth of half of a full DisplayPort 1.2 output.  That's enough bandwidth for a single 4K 30 Hz display or dual 1080p 60 Hz displays (or a single 2560x1600 60 Hz display), but it's not enough bandwidth for a 4K 30 Hz display and a second 1080p display simultaneously.  Again, I describe this in more detail in the thread I linked in my first post.

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mockgeek
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Re: Regarding: HDMI Dual Monitor USB-C Hub

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So, you are really saying that the USB-C port would really need to be isolated to video output (and maybe power) but not for handling the traffic associated with other USB devices at the same time?

Would the TB16 work for me if I wanted to use Display Port for the 4k and HDMI for the 1080p? Or does the lack of Thunderbolt support of the 7378 disqualify that hub? Or are you saying that the Thunderbolt option on that hub would not be something I could use?

As for the 30 Hz vs. 60 Hz, I have been using this 4k at 30 Hz long enough to not be concerned with any jitters with motion. I use this laptop for work. Outside the occasional YouTube video, I am mostly in terminal windows most of the day along with browsers on mainly static pages. I mean, I wouldn't ignore the 60 Hz option if it was available, but I can live without it.

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jphughan
5 Tungsten

Re: Regarding: HDMI Dual Monitor USB-C Hub

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@mockgeek wrote:

So, you are really saying that the USB-C port would really need to be isolated to video output (and maybe power) but not for handling the traffic associated with other USB devices at the same time?

Would the TB16 work for me if I wanted to use Display Port for the 4k and HDMI for the 1080p? Or does the lack of Thunderbolt support of the 7378 disqualify that hub? Or are you saying that the Thunderbolt option on that hub would not be something I could use?

As for the 30 Hz vs. 60 Hz, I have been using this 4k at 30 Hz long enough to not be concerned with any jitters with motion. I use this laptop for work. Outside the occasional YouTube video, I am mostly in terminal windows most of the day along with browsers on mainly static pages. I mean, I wouldn't ignore the 60 Hz option if it was available, but I can live without it.


As I described in the thread I linked, if you have a device that attempts to carry both display data and USB 3.x data, your display bandwidth gets cut in half.  Power is carried over separate pins, and in fact USB 2.0 is also carried over separate pins from the high speed lane pins that can get used for display traffic or USB 3.x, so you could theoretically run power and USB 2.0 and still have maximum video bandwidth, but typically adapters like the ones you have want to run traffic on USB 3.x because USB 2.0 would become a bottleneck for things like Gigabit Ethernet.

You can't use any devices that require Thunderbolt 3 if your system doesn't actually support Thunderbolt 3.  From what I'm seeing, your system doesn't have Thunderbolt 3, so those options are out.  Intel recently released a newer Thunderbolt controller meant to be incorporated into peripherals that would allow such peripherals to be backward compatible with regular USB-C, but I don't know if that's been incorporated into any actual products yet, and in any case the backward compatibility would come with reduced functionality, so it wouldn't solve your problem even if the TB16 had that controller.  But the TB16 doesn't have that controller; it requires Thunderbolt 3 support from the system, otherwise it doesn't work at all.

If you want to run a 4K 30 Hz display and something else, your best bet is probably the Dell D6000 dock.  It's normally not ideal for the reasons I described in the thread I linked in my second reply in this thread, but if you're ok with a 30 Hz refresh rate, you might also be ok with (or not even notice) the limitations of DisplayLink technology.  The D6000 can support up to 3 simultaneous displays all running 4K 60 Hz, and it offers USB ports, Ethernet, and charging.  The only potential catch is that the DisplayLink technology it uses requires drivers, and the only Linux distro I see drivers available for on DisplayLink.com is Ubuntu.  If you're running that, fantastic.  If not, then I'd do some digging as to whether DisplayLink is somehow available on the distro you're using.

The other option would be a USB-C DisplayPort MST hub like this one, which would dedicate your entire USB-C interface to video and therefore allow enough bandwidth to run a 4K 30 Hz display and a 1080p display simultaneously, and natively from the GPU rather than via DisplayLink.  (Note: Those MST hubs are available with either DisplayPort or HDMI outputs.  If your display setup means you need one of each, then buy the DisplayPort version and then get an active DisplayPort to HDMI adapter.  The cheaper and more common passive adapters and simple DisplayPort to HDMI cables don't always work with MST hubs and similar devices.)

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mockgeek
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Re: Regarding: HDMI Dual Monitor USB-C Hub

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Thanks for the help! I'll look over these and plan my course of action.

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