X370 Gigabyte, 3950x cpu
EDIT...These M.2s are NOT for booting the pc.
The 8x slot will not let the pc boot with a 2TB Intel M.2 stick installed.
A 1TB WD M.2 stick works.
The bottom 4x slot works with everything...1TB and 2TB sticks.
I tried two different cards and both had this problem with the 8x slot.
I thought my cards were defective till I tried the 1TB sticks. Then thankfully found that the 4x slot worked properly.
And for anyone else wondering... the 4_M.2 stick Asus card that is for Threadripper will work here but only the bottom M.2 stick will show up.
At least I get a really good heatsink for the 2TB Q-Intel M.2...It slows down badly with a 50 GB file transfer.
Down to hard drive speeds then to <20MB/s - the speed will now go back and forth several times minute (20/150/20/150) as it cools and heats.
I'm hoping the Asus card heatsink will stop this.