Thank you everyone for the helpful posts in this thread. I picked up a Dell branded Connectx-4 LX (p/n 0MRT0D) recently and was able to successfully flash to the stock Mellanox firmware (14.32.1010, PSID MT_2420110034).
Unfortunately the Mellanox firmware produces an issue with the link LEDs on the card. They remain illuminated green even when there were no transceivers installed. The activity LEDs still worked correctly. Everything else on the card seemed to work normally but I was left wondering if there were any other not so obvious issues from the firmware change.
I ended up flashing back to the original Dell firmware. Thank you AK360 for including that flint command to back up the original firmware! I can confirm that restoring from it works. The LEDs on my card are now back to operating as they should. I also noticed that I did not have to manually set the GUID and MAC again after flashing despite the Mellanox to Dell PSID change.
Curiously the latest Dell firmware is a bit newer than the latest Mellanox one (14.32.2004 vs. 14.32.1010). Unfortunately the release notes Dell provides leaves the feature summary and fixes sections blank so who knows what difference it makes. I did catch that the UEFI driver was incremented up from 14.25.17 to 14.25.18 as well:
If anyone with a Dell branded Connectx-4 LX that needs to go back to the original Dell firmware and did not make a backup, I found that you can extract out the firmware from the Windows installer on
Dell's site. Use 7zip on the exe and you'll find the .bin in the payload folder. There are few but Dell helpfully includes the applicable part numbers in the filename: fw-ConnectX4Lx-rel-14_32_2004-
020NJD_
0MRT0D_Ax-UEFI-14.25.18-FlexBoot-3.6.502.bin.