LG 27UD88-W flickering w/ Intel NUC over USB-C

[Mr.Humble]

Hi everyone,

 

I recently bought a new monitor for my dad, the LG 27UD88-W (4K, USB-C, adjustable stand etc.). He was using it with his home office PC for a while over HDMI, no issues except for his old and tired GPU not being able to output 4K.

 

So yesterday I installed it in his office where he has an Intel NUC 7i5BNK (or something like that) that has Thunderbolt 3 over USB-C port. I plugged it in using the C-to-C cable provided with the monitor, and shortly this strange thing started to occur every couple seconds.
 

The monitor momentarily flickers. It's not image flickering, more like the monitor loses signal for a second and then gets it back up. This happens randomly every couple of seconds, rendering the monitor basically useless and potentially making it an epilepsy hazard.

I tried searching online and discovered one article where the person was trying to hook the monitor up to the 12" Macbook with the same issue, who solved it by attaching a different C-to-C cable. Some other users reported similar issues with monitors plugged into the USB-C port of an Intel NUC, which in some instances was solved by changing the refresh rate to 30Hz - a valid option since the monitor is to be used for office work, but unfortunately one that doesn't work at all in my case.

 

I updated the Thunderbolt drivers, installed the LG monitor drivers on the office PC, tried (unsuccessfully for some reason) to update the BIOS (another suggested solution) and started downloading other updates and drivers so that I can investigate further. Unfortunately I can only work on this after dad closes the office and since I also needed to perform a system backup and the internet in his office is not exactly lightning fast there weren't many updates that I actually managed to install.

Apparently Windows itself is somewhat aware of the connection issues since each time after logging in a message "a USB device may be limited due to connection" or something along those lines pops up and directs to a Windows help page where various type C connections and troubleshooting steps are described.

I'd also like to point out that connecting the monitor over both USB-C and HDMI solves the issue (the input is still USB-C - verified that) and the PC thinks there are two monitors.

I'd  like to hear from you guys, has anyone experienced similar issues with this particular monitor, or with monitors connected via USB-C to an Intel NUC? Could it be the cable? Could it be the NUC? What do you think I should do? Can you suggest some troubleshooting steps?

Also (I know it's a long shot) I think LMG uses these monitors (a lot of them), did anyone there experience this issue? @jakkuh_t @James @nicklmg
 

I'll be grateful for any suggestions and tips, and if you managed to read this far, thanks for your interest.

 

Sincerely,

 

Vojta

[Glenwing]

The most likely cause is that the cable cannot handle the amount of bandwidth that 4K 60 Hz requires. The data cannot reliably reach the other side, resulting in only intermittent video. Look for a USB-C cable rated for 20 Gbit/s.

[mal_a_woot]

Heya Vojta

 

I got the same monitor a couple of weeks ago.  The USB-C connection on mine has been fine, however when connected via DisplayPort it did a stuttering thing which sounds similar to what you are describing.

 

Changing the cable fixed my issue, so it may be worth trying it with a different 20 Gbit/s USB-C cable IMHO. 

 

Hope you get it sorted. 

 

Cheers

[Mr.Humble]

Hey guys, I've got some updates to the situation.

 

I've spent a while waiting for the cable to arrive (apparently in Czech Republic no major tech retailers tend to keep a large stock of 30€ cables) and trying the monitor with it.

 

I also tried disconnecting all peripherals from the monitor and plugging them back to the NUC directly, which seems to have had some positive effect, however can't say how great since I don't have physical access to the monitor anymore (Monitor is in my father's office I'm in a different city for uni)

 

Unfortunately neither seems to have solved the issue as it's still going on.

 

One thing that occured to me is that the issue might be memory related. The NUC is outfitted with 1*8GB DDR4 memory stick from Kingston, of which (if I understand it correctly) 4 GB are shared with the integrated Intel GPU. When simulating a typical workload the system hit about 3,8 GB of system memory usage.

 

 

I'm frustrated and at a loss. Do you guys think it's an issue with the monitor itself and I should RMA it? Or could increasing the RAM help?

 

Note that we neither own nor have easy access to any other devices with DisplayPort over USB-C / Thunderbolt 3, so there's no way to test teh Type C connection with a different configuration, and my father's home desktop is Sandy Bridge based and neither it's iGPU nor the AMD HD5770 support 4K at all, so I can't test the regular DisplayPort input at 4K. Also I know it's stupid, but I really can't remember if we tested it at FHD, so I'll do that and update this thread.

 

I'll be grateful for any suggestions

 

Cheers,

 

Vojta