This is a bios provided by asrock support to solve nvme compatibility.It enables a menu in storage configuration (FORCE_SATA,FORCE_M2).Without this bios mod my kioxia exceria nvme drives would only be recognized on M2_3 slot(the top one in this case).Now they both work on M2_1 and M2_2 slotshttps://mega.nz/file/E2pDUDzQ#Kw2tXo-pvnC1gHyTZLcw7uycZoQ–RcpuQlMx7y6hPk
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I recently fell foul of an Asrock M.2 issue.
Purchased an SN850x for my system that can’t be detected in the M.2 Slots at all. I have to use it in my second PCIe slot that shares lanes with the GPU 
FYI
https://www.asrock.com/support/qa/Technical%20NNotes%20-%20Storage%20Device%20Compatibility.pdf
Good luck with your drives everybody
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