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idata
Community Manager
1,807 Views

Reliable Type C to Display Port cable with MST support [NUC7i5BNK]

Hi Everyone,

I became a first time NUC owner as of yesterday

I have a NUC7i5BNK running Fedora 28. My work setup consists of 3 Dell U2415 (1920x1200, MST bandwidth required in total is 13.86Gb/s) displays connected via DP daisy chaining. The setup worked just fine with my Windows desktop using a DP cable, but I'm having issues getting things working with the NUC and a type c to DP cable.

Rarely do I get all 3 displays to show up, usually all 3 are black and then go to no signal. Sometimes they constantly flicker as if the display manager can't figure out what to do with them or the cable is intermittent. The BIOS reliably shows up, but mirrors across all 3 displays. When I initially installed the OS, the NUC was only connected to one monitor.

Here's the current cable I'm using: https://www.amazon.com/gp/product/B01N11K30W Amazon.com: USB C to DisplayPort Cable 4K@60Hz, CHOETECH USB 3.1 Type C to DP Cable Thunderbolt 3 Port Compatible with 2…

I believe the culprit to be the cable itself, and I was wondering if anyone else here has had luck with a C->DP cable and using MST. If someone could point me in the right direction that'd be awesome!

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5 Replies
Leon_Merts
New Contributor II
212 Views

Hi aijorgenson,

I can not test this (don't have a third 1920 x 1200 monitor), but the USB-C (DP1.2) is as far as I know bound to the USB 3.1 speed which is 10 Gbps.

On a system with a "normal" Display port the bandwidth is higher. DP 1.0/1.1 up to 10.8 Gbps / DP 1.2 up to 17.28 Gbps / DP 1.3/1.4 up to 32.4 Gbps.

Although not a solution, a quick check / solution would be lowering the resolution of the displays connected to the USB-C.

Regards,

Leon Merts

idata
Community Manager
212 Views

Hi leon,

Thank you for your insight! I'm not sure what sort of wizardry is going on but I did the following and have gotten it working(who knows for how long):

  • Disabled the Thunderbolt 3 controller in BIOS
  • Reset all of the displays
  • Added them individually, in the order that they occur in the link by initially disabling DP 1.2 in all of them and then going through and reenabling it

I've rebooted several times. I've gotten the concerning black screen, but then the display manager managed to figure things out on its own. It wouldn't surprise me if it bricks itself in the near future, but clearly bandwidth isn't a concern if it's running all 3 displays in 1920x1200.

n_scott_pearson
Super User Retired Employee
212 Views

No solution, but I am curious: What if you use Windows? Does it work then (i.e. is this a Linux driver issue)?

Regarding a solution, what about using a 3-port MST hub?

...S

idata
Community Manager
212 Views

Hi Scott,

I've considered using a 3 port MST hub to just remove the complications of daisy chaining all together, but I can't seem to find one with good reviews. It doesn't help that they start at ~$90+. I don't want to make a purchase that large unless I'm confident that it will work.

I could try a windows install for troubleshooting, the downside is that putting Windows on the NUC defeats the entire purpose of why I bought it. I might do a test install if the problem persists.

n_scott_pearson
Super User Retired Employee
212 Views

I have this adaptor: https://www.amazon.com/gp/product/B06XPVGQKY Amazon.com: USB-C to HDMI Adapter - 4K - 2 Port MST Hub - Thunderbolt 3 Compatible. If I use it with two 1080p@60Hz monitors, it works just fine. But, if I substitute in a 4K TV for one of the monitors, I end up with a disconnected TV. This jives with the Leon's assertion.

I can't argue with the pricing concern; it's definitely a spendy option. As for reviews, if you are using Amazon, the reviewers are mostly pinheads and you have to look at the reviews with a grain of salt. Many of the poor reviews are idiots blaming the adapter for problems that are bugs in Windows or the Intel HD Graphics driver (good example: monitors changing order across sleep cycles; that's not the adapter's fault!).

...S

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