 Microsoft's EFI FAT32 specification states that any FAT file system with less than 4085 clusters is FAT12, else any FAT file system with less than 65525 clusters is FAT16, and otherwise it is FAT32.The entry for cluster 0 at the beginning of the FAT must be identical to the media descriptor byte found in the BPB, whereas the entry for cluster 1 reflects the end-of-chain value used by the formatter for cluster chains (0xFFF, 0xFFFF or 0x0FFFFFFF).The entries for cluster numbers 0 and 1 end at a byte boundary even for FAT12, e.g., 0xF9FFFF for media descriptor 0xF9.