[NAME] , the question from OP is which one to set RAID or ACHI (which is typo of AHCI).  By pointing that my response is incorrect, the other choice is RAID.  Would you elaborate why RAID is the correct settings?  OP has indicated that he/she not asking for anything else, just which one to choose. It's hilarious that almost everyone in here always advised to change the settings to AHCI, but when it comes from me, it's incorrect.  
What is the correct BIOS setting for NVME SH810 WDC SSD? (Drive C:)  (it has a drive but that is a nomral drive)RAID or ACHINew computer and the drive seems rather slow to the XPS 8930. Dell has it set in the BIOS to RAID out the box.If it should be ACHI can I change this in BIOS with out any issues to the Apps and data on C:?
XPS 8930, correct BIOS setting for NVMe SH810 WDC SSD?