(Cross post from r/macpro, sorry for those who already seen this post...) Hi guys, I'm currently having read and write speed issues using an NVMe U.2 SSD through a PCIe adapter. Using Blackmagic Disk Speed Test, I get a little more than 500MB/s write speed and around 420MB/s read speed which is too low for the kind my SSD. In comparison, the same drive and adapter gets more than 1000MB/s read/write in a linux based PC (don't know the exact figures, it's just way higher than in macOS). I tried benchmarking while booted up in a separate drive and also while booted up directly on this drive. I also tried all the PCIe slots with no luck. The is working in 5gt/s (whatever it means ?!) in 4x mode. I initialy tried with macos HS with bootrom updated but didn’t make any changes to the speed reported by Blackmagic DST. Here is my setup: cMP 4,1->5,1 with fully updated firmware running Mojave INTEL SSD DC P3605 1.6TB (SSDPE2ME016T4S) with firmware fully updated (RA14 I think) Startech PEX4SFF8639 I want to try out at some point booting up linux on the cMP and do the same benchmark and see if it’s an hardware or software issue. But before, does anyone have a clue on what to look for ?