TB4/USB-C Ports on Laptop

Hi guys, a bit of a history to this one and it ties back into the last time I posted here for a similar issue - about 3 years or so ago.

Anyway - back in July 2022 I purchased the ASUS Zenbook Space Edition laptop. Great machine but ran into issues using it with my Plugable dock. I spent months trying to troubleshoot it , even getting a new dock sent to me by Plugable. I thought initially that it was somehow tied to the whole modern standby stuff, then figured it must have just been the laptop's ports that were dodgy since re-installing Windows twice from scratch never fixed the issue.

Sadly I stopped using the Zenbook after a few months and it became a rather expensive 'mistake' because I couldn't get any stability out of it - I shelved it and its never really been used three years since. A couple of weeks ago - randomly I started thinking about this problem again, and threw it at ChatGPT. Gave it a descrption of all the hardware involved, and the problems encountered.

It spat back at me that it was 95% certain it was a display link problem. Apparently, Plugable docks rely on DisplayLink chips, which don’t use the GPU’s native video output. Instead, they compress video in software via the CPU and then send it over USB. When the CPU then comes under load, or something that requires power draw (like charging the laptop), the video stream collapses. The external screen would flicker, blackout and then reset. A minute or two would pass and it would happen again. Another few minutes, and again. It was more stable when the laptop wasn't charging, but as soon as I put any real load on the CPU or do something even a tiny bit heavy, boom the screens would blank. It just wasn't sustainable. I wasn't aware of this particular issue, and at no time did Plugable's support team mention it could be the issue - why would they? To do so would mean they would have to admit the core tech in their product doesn't really work properly (or at least didn't 3 years ago)

The 'solution' was to get something proper USB-C that could run in AltDisplay mode. So, since I was planning on getting a new monitor anyway - I jumped on it. Got one of the Dell 34" Ultrawide screens with the USB-C hub capability. Its been flawless with the Zenbook, not a single issue. So it seems that ChatGPT 'fixed' an issue I just couldn't resolve at the time and given the Zenbook a second lease of technical life. Kudos to the AI haha!

That being said - it HAS uncovered another issue. More to do with the Thunderbolt 4 ports on this model laptop. There are two of them on the left side of the chassis. The top port is flawless with the Dell monitor, no issues during regular operation or charging the laptop. The lower port however, while it charges the laptop there is no video stability whatsoever, with the screen flicking on and off and glitching and resetting every three seconds like clockwork. Now, my understanding of this laptop's specs was meant to be that BOTH ports support power delivery/charging and video. Experience with this new Dell screen however would indicate only one of the ports is actually capable of doing this. This issue replicates a problem a user was having for one of our clients a few weeks ago in a similar setup. It was one of the Dell Latitude 5400 laptops, two USB-C ports on the side but only one of the ports is marked for power delivery. I told the user he was using the wrong port basically. When you use the port marked for power delivery - there's no external screen issues. When you try and use the other port, the laptop actually complains that the port in use isn't suitable etc etc.

I do apologise that this has been a long winded post and I've taken time to get to the point, but my question basically is: Despite my Asus having two TB4 ports that are supposed to be exactly the same, is there anyone, anywhere who knows or can confirm if only ONE port actually works to provide power delivery/charging? Has anyone experienced anything similar?

*If you've read all of this I truly do thank you for your time

Matchwood

This kind of intermittent problem is usually caused by wear on the USB-C connectors. The best option short of replacing them is applying a little pressure with a pliers to tighten them up again.

I have a different take on this....

Are you relying upon the USB port to not only supply video to the monitor but also power? It's typical for a USB-C port on a laptop to not provide enough power to the monitor, thus causing it to cut off and come back on again. Typically, a monitor with USB-C video input will have another means of powering the monitor such as plugging in another USB-C cable that you then plug into a USB charger.

You can also try turning the volume way down or off on the monitor (often that alone is enough) and turning the brightness way down. This is only meant as a test, not a permanent solution.

hsehestedt said:

I have a different take on this....

Are you relying upon the USB port to not only supply video to the monitor but also power? It's typical for a USB-C port on a laptop to not provide enough power to the monitor, thus causing it to cut off and come back on again. Typically, a monitor with USB-C video input will have another means of powering the monitor such as plugging in another USB-C cable that you then plug into a USB charger.

You can also try turning the volume way down or off on the monitor (often that alone is enough) and turning the brightness way down. This is only meant as a test, not a permanent solution.

Click to expand...

Yes - because it does both. Dell's specs confirm this monitor provides 90W power delivery/charge, that's why the monitor is also called a USB-C Hub variant and why I purchased it. I've been able to eliminate the physical docking station from my desk, and now just run a single USB-C cable from the monitor into the laptop, and use the ports the monitor actually has for any additional peripherals. The monitor itself is now my dock.

My question was more to do with the laptop and see if anyone can confirm that, despite Asus's claims, only one port will actually work and provide that functionality. As I say, based on the experience with a client the other day and his Dell laptop, only one of the ports was marked to provide power delivery, and it was that port that worked fine with his external screens.

Matchwood said:

My question was more to do with the laptop and see if anyone can confirm that, despite Asus's claims, only one port will actually work and provide that functionality.

Click to expand...

Clearly that is not the case or you would not get any video out of that port at all. If you see video even for a second, then that port has DP Alt mode support. There would be zero reason to provide that support to a port not intended to actually work that way.

What does ASUS have to say on the matter?