Ok i can reproduce the issue using the pc6.mbr posted by bouke: cp pc6.mbr disk.img # otherwise parted complains "Can't have a partition outside the disk" truncate -s 600GB disk.img
# fdisk correctly detects the msdos partition table fdisk -l disk.img Disk disk.img: 600 GiB, 644245094400 bytes, 1258291200 sectors Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disklabel type: dos Disk identifier: 0x44a777ed Device Boot Start End Sectors Size Id Type disk.img1 * 2048 718847 716800 350M 17 Hidd disk.img2 718848 975747071 975028224 465G 7 HPFS disk.img3 975747072 976771071 1024000 500M 27 Hidd # parted fails parted disk.img print Disk /home/manu/Téléchargements/disk.img: 644GB Sector size (logical/physical): 512B/512B Partition Table: atari Disk Flags: Number Start End Size Type File system Flags 1 8323MB 14,8GB 6446MB primary boot Also using the disktype utility (which knows both msdos and ahdi) the msdos partition table is properly recognized. CCing John as he is the original atari patch author @john: I am heavily suspecting here the disk signature, but maybe you have a better idea ?