RE: XPS 15 9550, Thunderbolt NVM firmware issue with Thunderbolt 3 to 2 adapter
Per the Thunderbolt software “settings” page of the respective systems (screen capture below), both the Dell XPS 15 9550 and the Intel NUC6i7KYK are using the same Thunderbolt Controller generation, “Thunderbolt 3 (1575)”, hardware.
However, compared to Intel, the firmware support that Dell is offering is behind in both the NVM firmware version (NVM 16.00 vs NVM 18.05) and the PD firmware version (PD 1.02.06 vs PD 1.07.00).
As you can also see in the below driver settings screen capture, because Dell has not updated their Thunderbolt 3 firmware, some functionality (such as “External GPUs Supported”) doesn’t exist on the XPS 15 9550, while it does on the NUC6i7KYK.
Since I have both systems, I can also tell you that the above mentioned Apple TB3-TB2 adapter works fine on my Intel NUC6i7KYK, but just gives a USB error when plugged into my Dell XPS 15 9550.
Looking at Intel's driver download page --
https://downloadcenter.intel.com/download/26141/Thunderbolt-3-Firmware-Update-Tool -- the NVM 18 firmware was released by Intel for the NUC6i7KYK way back at 7/15/2016.
When is Dell going to release this long overdue firmware update?