msi slotB key slot for ‘B’Key card (also known as Socket 2) (SATA) M key slot in ‘M’Key card (also known as Socket 3) (PCIe x 4) B+M Key cassettes are available for both cassette slots. Check HDD and SSD support specifications.DIMM Slots; Max Memory (GB) PCI-E x16; PCI-E Gen; PCI-E x1; SATAIII; M.2 Slot; TPM (header) USB 3.2 ports (Front) USB 3.2 ports (Rear) USB 2.0 ports (Front) ... MSI,