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My notebook (Dell Precision 5520) has Thunderbolt 3.

Thunderbolt 3 provide 40Gbps (double the speed of Thunderbolt 2).

In terms of video it has 8 lanes of DisplayPort 1.2 (High Bit RTE 2 (HBR2) and MST).

It should support two 4K 60 Hz displays. But I don't need 4K screens. I need Full HD screens, but I need not 2, but 3 of them.

When I look at specifications for Docking stations, I see that those of them that provide 3 screens require "HBR3 or Displayport 1.4" or "DP1.4 with DSC"

My question is - will I have a 3 screen docking station working from my Thunderbolt 3?

Because from the bandwidth perspective it sounds like more than enough for 3 FullHD screens. And 8 lanes of DisplayPort 1.2 should cover 3 screens.

But, maybe there is another reason to request HBR3 or Displayport 1.4 to work with these docking statins?

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  • Can you please edit your question? As it is written now, it is not really clear what you're asking.
    – Irsu85
    Jun 1, 2022 at 5:47
  • Even though the bandwidth is there to stream the pixels for 3 1080p screens, the DisplayPort 1.2 protocol does not have a way to "pack" more than 2 screens over the connection. That is why you need DisplayPort 1.4, because the protocol has been upgraded to provide additional functions and raise the limits on number of display & audio streams.
    – Romen
    Jun 1, 2022 at 14:25
  • @Romen, yes, but Thunderbolt 3 has 8 lanes of DisplayPort 1.2 Jun 2, 2022 at 3:26
  • You are misunderstanding what "lanes" are. They are not the same thing as individual display connections. One display will need multiple lanes (usually 4) and the way DisplayPort 1.2 works can only divide those lanes in certain ways. It is very likely that DP 1.2 doesn't support 3 monitors because it wasn't designed to divide 4 lanes into 3 displays, and Thunderbolt 3 having 8 lanes is actually not part of the DP standard.
    – Romen
    Jun 2, 2022 at 14:31
  • Thunderbolt 3 - having 8 lanes of DisplayPort 1.2 is not a part of not part of the DP standard, but it is a part of Thunderbolt standard thunderbolttechnology.net/blog/thunderbolt-3-usb-c-does-it-all Jun 3, 2022 at 2:03

2 Answers 2

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  • Thunderbolt 3 Bandwidth: 40 Gbps
  • 24-bit, 1080p @ 60 fps: 24 × 1920 × 1080 × 60 = 2.98 Gbit/s
  • 24-bit, 1080p @ 144 fps: 24 × 1920 × 1080 × 144 = 7.17 Gbit/s
  • 24-bit, 4K UHD @ 60 fps: 24 × 3840 × 2160 × 60 = 11.9 Gbit/s
  • 48-bit, DCI 4K @ 144 fps: 48 × 4096 × 2160 × 144 = 61.1 Gbit/s

I use this Lenovo Dock every day to run three screens over Thunderbolt 3. However, like many others, it's a mix of HDMI and DisplayPort. This one has 2 of each and it can only drive 3 at a time. My laptop seems to have an additional limitation (probably not enough video memory), where it can only drive 3 displays, so if I plug 3 displays into the dock, the laptop screen will turn off.

If you can use DisplayPort, you can use the one I linked, or a cheaper one. If you want HDMI only, you could try using a hub like this, and a couple of these USB to HDMI adapters. I can't guarantee this will work, but thunderbolt 3 does have enough bandwidth for 3 FHD displays.

Edit: DisplayPort 1.4 and HBR3 are ways for your dock to drive higher resolution or higher refresh rate monitors. It only effects the connection between the dock and monitor. They will make NO difference if you are running 1080p (FHD). DisplayPort 1.2 offers support for 1080p up to 240hz.

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  • Please, check out my answer, it has a few more things expleined Jun 6, 2022 at 3:05
  • So you are using Lenovo ThinkPad Thunderbolt 3 Dock Gen 2 135W (40AN0135US) . I like it Jun 6, 2022 at 3:14
  • Yes, the 40AN works great for 3x 1080p screens, and 1Gbps Ethernet. I really like the extra thunderbolt input and headphone on the front.
    – Alphy13
    Jun 8, 2022 at 16:03
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I bought Dell Thunderbolt Dock (WD19TBS) it worked fine. It allowed me to utilize 3 FullHD displays just fine. It was actually more than FullHD, it was 1920x1200, thus the Thunderbolt-3 can do it.

But there was a catch. My notebook (Dell Precision 5520) can only run 3 displays. So if I use 3 external displays with my docking station, my laptop display is getting turned off.

My notebook (Dell Precision 5520) is not the only one suffering from it. It is a new trend, new laptops these days have kind of 2 video cards. In my case it is Nvidia Quadro M1200 with 4Gb of video memory and Intel HD Graphics 630 with shared memory. Nvidia Quadro M1200 - designed to have no video outputs, it works like a "slave". Intel HD Graphics 630 - is a "master" in this context. So the "master" sends all the heavy calculations to be processed by the "slave" and only displays what is returned by the "slave". Thus, even having 4GB of video memory and "Nvidia Quadro" on board, the overall configurations still limited to the number of screens that the "master" video card can provide.

Lucky we have displaylink on the market, they make chipsets that work like external video cards. For example DL-6950 chipset has 2 outputs, the maximum resolution is 3840x2160 (UHD) if both video outputs are being used. This chip is used to build a number of Adapters. Popular Startech USB32DP24K60 USBA2DPGB and little known ELECABLE

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