I found this ("The two internal M.2 2280 storage slots support PCIe SSDs with one supporting SATA as well.") and that ("I remember someone who did try putting sata type m.2 on the left M.2 port and it didn't work, only the right m.2 supporr sata/nvme. 2230 and 2280 is the length of ssd drive."). So the two slots seem to be different, indeed.
Hello friends, I just realized that the two M.2 slots inside my DELL XPS 9700 are perhaps not identical: on the metal cover above the first slot it is written "2280 SSD1 (SATA + PCI-E)", and on the second one it is written "2280 SSD2 (PCI-E)". In the documentation, this is not mentioned: [URL] Can you confirm that the two slots are different, or are the labels just misleading? Thanks, Daniel
Two M.2 slots inside XPS 9700, first one "SATA+PCI-E", second one "PCI-E"