I recently bought an XPS 15 9500 (with UHD+ display), and I noticed that when I connect my external 4K 60Hz display to either of the left-side USB-C/Thunderbolt 3 ports (via a USB-C to DisplayPort cable), the monitor flickers on and off, intermittently displaying my desktop, showing "No Signal", or trying (but usually failing) to re-establish the connection. I would describe the behavior as similar to what I'd expect if the cable were faulty/loose. However:
Note that in all cases, even though the monitor doesn't have a stable signal, Windows does correctly recognize all of the monitor's available resolutions and refresh rates.
On my XPS 15, I've tried the following:
Does anyone else have the same issue, or does anyone have any other ideas for things to try before I give up and send the laptop back?
@ingjald This might be related to the issues that are being reported with the also-new XPS 13 9300. That system is generating all sorts of reports of issues using Thunderbolt peripherals and docks, and a recent BIOS update seems to have completely broken the ability to use certain USB-C to DP and USB-C to HDMI adapters/cables that worked perfectly fine on older BIOS releases. Based on your test results and what you've tried thus far, I'm guessing this is going to be a BIOS or TB3 controller firmware issue that hasn't been fixed yet. So if keeping the display connected to the non-Thunderbolt port on the right isn't an acceptable workaround for you (or you don't want to risk ending up past the return period and putting up with this issue for an indeterminate time), then unfortunately I would consider sending the system back. Sadly there aren't exactly a lot of XPS 15 equivalent systems out there. Its only real competitor in the PC world is the X1 Extreme Gen 2. I did a small comparison of those two systems here if you're interested.
@jphughan, thanks for your response!
I suspect you may be right. After reading your response, I booted into Ubuntu again, and the monitor did the same thing as it does in Windows—I guess I just got lucky on my previous boot into Ubuntu. I also tried downgrading the BIOS to the only other available version, but the behavior is the same.
That said, I'm curious to see if anyone else has the same issue (or conversely, if anyone doesn't have the same issue). While I don't mind the workaround for now, I can't rule out a hardware issue, and I certainly wouldn't want to find out that it is a hardware problem after the return period has run out.
As another update to this, it looks like the problem is much less severe when the charger is plugged into the other left-side USB-C port. Even then, though, the connection to the monitor is not stable.
Again, this all seems consistent with the issue that folks have reported on the XPS 13 9300.