Downloaded the newest Thunderbolt driver this morning. It MAYBE fixed the occasional outage problem that many are having with Thunderbolt/USB-C port adapters - jury is still out on that.
Here is what it DID NOT FIX: The fan speed. No matter what I plug in to that port, the fan revs up and stays up.
I disconnect all USB-C adapters and revert to my USB 3.0 equivalents and everything works fine. I have a 3.0 LAN/Gigabit port and a Plugable 3.0 to HDMI adapter that are working great with no fan revving.
The minute I use my USB-C versions, that fan gets spinning. Why? Watching my Task Manager, I can see 1-4% CPU, 20% Memory, 1-7% disk. There is NO REASON for that fan to be running.
Until Dell and Intel get that Thunderbolt port dialed in, I'm staying on good ol' USB 3.0. At one level, that is frustrating as I bought the XPS 15 partly because of the promise of the "One port to rule them all."
I agree 100%. Bottom line is that ThunderBolt 3, at least in the XPS 15 9550 implementation, is not ready for prime time.
Right now I am running with my XPS 15 closed using an external monitor connected to the integrated HDMI port, a USB 3 adapter into which I have plugged my gigabit ethernet, my usb keyboard, and my integrated monitor webcam. I also have my wireless mouse dongle connected to one of the integrated laptop usb ports and have my power adapter connected. Fan is completely silent and everything works perfectly. I should be able to connect all of that thru the TB15 dock using the single Thunderbolt 3 connection to the XPS 15 9550 with exactly the same results. Unfortunately with the current state of drivers I cannot.
I bought my TB15 dock directly from Dell. Their can't be that many of us. You would think Dell would make the effort to make sure that all of us that did would be communicated to and taken care of...apparently not.
Have a precision 5510 (the workstation version of XPS 15) with exactly the same problem. So far the Thunderbolt dock is not usable due to annoying fan noise even when the machine is fully charged and idle.
I find it interesting that a 13" 9350 plugged into a dock won't ramp up speeds, but a 15" 9550 will ramp up speeds.
I called Dell for technical support on this but encountered unclear answers on whether it was going to be addressed or not:
Our resolution specialist got a feedback that the fan speed will be normal for the system type of your xps to reach the max speed for using your ac adapter when in thunderbolt, If there will be updates for this matter then we could wait for review either thunderbolt firmware or your system bios in the future.
The Thunderbolt TB15 has a normal behavior for the fan speed of XPS and any brand system with
Power Adapter Input Voltage AC 100~240 V.
So far, we can't answer about any updates from Microsoft / Dell firmware or drivers of the dockstation.
New Bios that may address this issue!
Fixes & Enhancements
Improved the system stability
Fixed system may not able to boot with external monitor with lid closed
Fixed USB audio/mouse may be lag while connecting to Dell Thunderbolt Dock (TB15) and Dell Dock (WD15)
Fixed Fan may be noisy while connecting to Dell Thunderbolt Dock (TB15) and Dell Dock (WD15)
Fixed Bitlocker Malfunction or Keeps Prompting Recovery Key every time reboot
I can confirm after testing for several hours that the XPS 15 9550 I have on hand:
1. Loses Ethernet connectivity. I've seen this happen after larger file transfer, or if the laptop is restarted.
2. Drops USB Keyboard/mouse functionality.
3. The fan speed on my 9550 is lower.
After several weeks of waiting, just returning it. It isn't ready for primetime.
And yes, I've followed all the Dell guides for attempting to make it work, including this recent BIOS update, reinstall of drivers, updated Windows 10 to latest versions, tried different laptops, etc. Probably one of the larger waste of times in recent memory.