Precision 5520 need to run triple monitor with 1x 4k @60hz and 2x 1080 @60hz.

Question

Hi,

I have a precision 5520. I recently bought a Samsung M7 4k monitor ( has 2 hdmi 60hz and 1 usb c input for display). I already had 2 1080p monitors (each has 1 hdmi and 1 vga port) which i connected using a usb C docking station with 2 HDMI. now I tried connecting the 4k monitor via laptop's HDMI port but it only works for 30hz, not 60hz. I found from other posts that i can run 4k at 60hz if i connect by usb c directly using usb c to hdmi 4k 60hz cable or usb c to usb c cable. The problem is that makes connecting 3 monitors impossible as I lose my only thunderbolt port to one monitor and only 1 hdmi remains so can't connect 3rd monitor. Is there a way to run all 3 at 60 hz, may be a thunderbolt dock? I also have a hdd which needs usb 3 port to be working (reading from other posts, i realised this might be concern if running 4k at 60 hz.)

Any suggestions for docking stations or adaptors would be great.

jphughan · Accepted Answer

Happy to help. The lowest cost solution here would be a Thunderbolt 3 to Dual HDMI 2.0 adapter. That will allow you to run two displays up to 4K 60 Hz each just from that adapter. So if you connect your 4K display and one of your 1080p displays that way, you'll be able to run the third display from the system's built-in HDMI output. Sabrent, StarTech, Sonnet, and Plugable all make TB3 to Dual HDMI 2.0 adapters, and they all have solid reputations for quality products.

If you want a dock, the Dell WD19TBS is your answer. It's the only current Dell dock that will deliver 130W to that system as it requires for optimal performance and also tap into enough display bandwidth to run your display setup. If you go that route, you'll need to connect the 4K display to the "downstream TB3" port at the edge of the dock, near where the system cable attaches, NOT the USB-C port near the HDMI output. As for the other displays, if those are the only inputs you have on the display side, then you should be able to use an HDMI cable for one and a DisplayPort to HDMI cable/adapter for the other. However, I've seen a few reports of typical passive DP to HDMI cables/adapters not working on that dock when two of them are use or when the dock's HDMI output is also in use. I have some theories as to what may be causing that, but the workaround is to use less common active DisplayPort to HDMI cables, which incorporate a DP to HDMI signal converter chip in the cable itself rather than relying on the dock's own DP output to switch to native HDMI signaling. Here is an example of the right kind of adapter.

Lastly, note that when you have three external displays in use, you will NOT be able to use the built-in display as well. On that system, the Intel GPU controls all display outputs, even if you have an NVIDIA GPU, and the Intel GPU in that system only supports up to three total independent displays.

jphughan · Accepted Answer

@droid_r10 Happy to help. In terms of the follow-up questions:

The 4K 60 Hz / USB 2.0 scenario occurs with a DisplayPort 1.2/HBR2 over USB-C system when using regular USB-C. With Thunderbolt, even a DP 1.2 system can run dual 4K 60 Hz and USB 3.x simultaneously.

You can use a regular USB-C cable with the dock’s Thunderbolt port, and you SHOULD use a regular USB-C cable unless the display itself supports actual Thunderbolt rather than USB-C. If it doesn’t support Thunderbolt, then a Thunderbolt cable would be a waste of money, and the less common active Thunderbolt cables actually won’t carry video over regular USB-C at all. The more common passive TB3 cables will carry video over USB-C, but again there’s no benefit when using a regular USB-C display. Length shouldn’t matter as long as the cable is actually rated for DP 1.2/4K 60 Hz and USB 3.x Gen 1. Right now the max cable length for that seems to be 2 meters except for active USB-C cables. If your display supports USB 3.x Gen 2, the max length is 1 meter. I only know of one active USB-C cable that can run DP 1.2 and USB 3.x Gen 2 up to 3 meters, but it’s more expensive.

On the WD19 dock family models, including the TB and TBS, the HDMI output and the USB-C output right next to it cannot be used for video output simultaneously.

The Precision 5520 only supports three total displays, regardless of how they’re connected. So no, you would not be able to attach a fourth display, in fact you would not even be able to keep the built-in display active when running three external displays. And you’d also have to be running Windows, since Linux doesn’t support completely disabling the built-in display, so it always counts towards your limit. The only workaround to this limitation would involve a USB dongle that used “indirect display” technology like DisplayLink — not to be confused with DisplayPort. But that technology comes with some drawbacks.

I don’t think you can run dual 4K 60 Hz + 1080p all through the dock simply due to bandwidth limitations on the GPU interfaces that are running across Thunderbolt, but I haven’t tested it. But when dealing with Thunderbolt, the max total GPU bandwidth available will still leave enough bandwidth on Thunderbolt to carry at least USB 3.x Gen 1 (5 Gbps) as well. The only way you could potentially bottleneck USB performance would be if you had an actual Thunderbolt peripheral attached to the dock that wanted to run PCIe traffic. You might want to read this explainer post I wrote about USB-C and TB3 where I focused specifically on how they work and how they affect available display setups.

droid_r10 · Answer

@jphughan  Can you please help out with this? I'll provide as much information as needed.

droid_r10 · Answer

Thanks a lot. So basically I looked up the TB3 to dual hdmi 4k 60hz docks but there don't seem to be any from Indian Amazon. I searched from your options but they are more expensive than the WD19TB....!!! has to do with import duty and taxes i think. So I guess my plan is set. I'll buy WB19TB. Now I have some follow-up questions for this dock.

1) I read in one of your previous posts that if a 4k 60hz display is connected, this basically downgrades all usb 3 ports to usb 2 speeds. (I may have misread this as this might be when connecting 4k 60hz via usb c rather than thunderbolt or maybe when we connect 2x 4k 60 hz through thunderbolt). Will this happen with my setup? As i have a hdd that will need usb 3 speeds to be active.

2) can i connect 4k 60hz monitor through thunderbolt port on dock using a usb c to usb c cable which supports 4k 60hz dp 1.2 compatible cable or it has to be thunderbolt 3 to thunderbolt 3? I can also get a usb c to hdmi cable for this but i have 2 usb 3.0 ports on monitor which i think will be useful if i connect the monitor using usb c to c, the monitor will act as usb hub. Also does the cable length matter?

3) is it true that the hdmi and usb c multifunction displayport which are side by side on dock are only either/or use case? Like i can't use both at the same time right?

4) is it possible to use a 4th 1080p display using the in built hdmi 1.4 port once i have 3 displays connected to dock?

5) What are the combinations that i can do with multiple monitor resolutions at 60hz while keeping usb 3 speeds intact? Eg. 2x 4k 60hz is Max or i can also connect another 1080 p monitor to that?

Apologies as I'm asking too many questions but I'm gonna have to invest big here for long term and i'd like to be sure of what all things this dock can/can not do. I one small dock initially when i only used 2 1080p displays and then when i bought this 4k monitor, bought second usb c dock which is non refundable and it only supports 4k@30hz (60hz if i reduce resolution to 2k) and now I'm stuck with 2 docks which are basically useless so you can imagine my cautiousness/frustration...!

Again thanks for all the previous posts you've done on similar topics. Lot of knowledge i gained from that which I'll be sharing with my colleagues.

droid_r10 · Answer

Thank you, you're literally a lifesaver.

I've ordered wd19tb, usb c to usb c dp1.2 cable for 4k and dp to hdmi active adaptor for using one of the display ports.

Thanks again, this was really helpful.

jphughan · Answer

@droid_r10  Happy to help, good luck with your setup!

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Precision 5520 need to run triple monitor with 1x 4k @60hz and 2x 1080 @60hz.

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