XPS 9300 with WD19 dock only displays 1 external monitor at 4k at 30Hz, not 60Hz

@jphughan thanks very much for the comprehensive response - appreciated.

I will keep a look out for the updated BIOS and hopefully that solves the issue.

I have also read about some of the problems with the 9300's USB-C ports so suspected this might be related.  Interestingly I couldn't connect the monitor directly to the 9300 with a USB-C-HDMI cable and when I called Dell technical support I was told it is not possible to use this laptop with an HDMI output (even with adapter) and I MUST use DisplayPort which I thought was odd.

Also, when I run the hardware scans in the 'Support Assist' software, everything runs fine apart from the "USB Composite" scan which says it was unable to run.  When I mentioned this to technical support on the phone they said not all scans apply to every laptop, so I should just ignore this.

As you say, hopefully the new BIOS update sorts out these issues.

Thanks.

@bs198  Happy to help.  Sorry to hear you got such bad information from Dell Support, although I can't say I'm surprised.  Just last week I saw a post here from someone who was told by Dell Support that their XPS 13 couldn't run 4K external displays because they ordered an XPS 13 with a 1080p built-in display, and they needed a 4K built-in display to run 4K external displays -- which is completely wrong.  USB-C to HDMI adapters/cables incorporate an active signal converter chip to switch the system's DisplayPort signal over to HDMI.  It is true that even apart from the current issues that seem to affect the XPS 13 9300 specifically, these active converter chips can be subject to interoperability issues.  I've seen multiple people who reported problems using various Dell laptops with USB-C to HDMI adapters even though they noted that the adapter worked fine with other systems.  After walking them through some basic troubleshooting, I basically said, "It's either a motherboard issue with your system [they didn't have another way to test USB-C video output] or an interoperability issue with that specific system and adapter.  Since the former would be a huge ordeal, you might want to try just getting another brand of USB-C to HDMI adapter.  Even though it shouldn't make a difference, it might."  I've made that suggestion about 5 times here now, and all 5 times that solved the issue.  Unfortunately not everything that SHOULD work in the tech world always DOES, and therefore sometimes changes that shouldn't make a difference will make a difference anyway.

Anyhow, it is absolutely NOT true that the XPS 13 9300 can't use any USB-C to HDMI adapters/cables at all.  In fact, the system actually wouldn't be able to tell the difference between that and a USB-C to DP adapter/cable in the first place, because again the system is always sending a DisplayPort signal anyway.  And even with the current XPS 13 9300 issues, there are some users reporting success using specific brands of USB-C to HDMI adapters.  I'd also be curious how that Dell Support person would explain the ability to use the WD19's HDMI output if the XPS 13 9300 didn't support HDMI displays....

As for the hardware scans, I don't use SupportAssist, so I'm not sure exactly what that test was, but I'm a bit skeptical of that answer that not all tests are applicable to all systems.  That may be true, but in that case I would expect that SupportAssist would say something like "Not applicable" rather than "Unable to run".  But I don't know that for sure.

Hi,

Any idea when the BIOS update will be available to XPS 15 9560?

In my case, the monitor is connected to my XPS 15 9560 directly throw an HDMI cable, and it can only work at 4k 60Hz. I also tried to connect the monitor a a WD 15 USB-C dock then connect the dock to my laptop through the USB-C port, and the result is the same.

I wonder if my laptop supports 4k@60Hz, because it is the old XPS 15 9560 which was released around 2017.

@rXtJ1RwL  You say that your display "can only work at 4K 60 Hz."  Did you mean to say 30 Hz there?  If so, that's expected in your setups because the XPS 15 9560's HDMI output is only HDMI 1.4, not HDMI 2.0.  You need HDMI 2.0 to run 4K 60 Hz, but that didn't arrive until the XPS 15 9570.  As for the WD15, that can only run a single display at 4K 30 Hz because of bandwidth limitations when using a regular USB-C dock rather than a Thunderbolt 3 dock.  If you got a WD19TB, which uses Thunderbolt 3, you'd be able to run dual 4K 60 Hz displays (or triple 1440p displays) because the WD19TB when paired with that system can tap into 4x more display bandwidth than a WD15 (or regular WD19).  I wrote an explainer post about this here.

@ links to members:
I have the same problem with my XPS 13 9310 and WD19 connecting to AOC U28P2G6B 4k monitor. Initially, when I first connect to the monitor it was able to produce 60Hz 4K resolution as an extended screen for XPS 9310, but on the next day it changed automatically back to 30Hz 4k, and I could not find a way to change it back to 60Hz 4K resolution. 
When I use the DA300 portable dock, it produces 60Hz 4k resolution on the same monitor.

I had a similar issue with my WD19 + Microsoft Surface Laptop 4. Enabling DSC on the laptop resolved issues for me.
See thread here:

https://www.dell.com/community/en/conversations/inspiron/wd19-dock-doesnt-output-4k-60hz-on-hbr3-system/647f9c1cf4ccf8a8de0253b8?commentId=647f9c51f4ccf8a8de06a80c