DOS ain't dead

YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) (Announce)

posted by ecm  , Düsseldorf, Germany, 30.09.2025, 20:07

MS-DOS v4 to v6 (and v7 in CHS mode) have to know the CHS geometry, and it may have to match what's found in MBR/EPBR/BPB.

> Btw I tried to manually create a primary partition that started at CHS 0,
> 8, 1 (LBA 504 that is 4k aligned) and CHS 1, 0, 1 but PQ magic still
> complained with error 105 or 110, so I don't try fit CHS alignment...

For my tests and the bootimg/partdisk.asm script I found that the most compatible thing is to start primary and logical partitions on a head boundary (CHS x:y:1), start extended partitions on a cylinder boundary (CHS x:0:1), and end all partitions on a cylinder boundary (CHS x:H-1:S).

Quoting from my sources: https://hg.pushbx.org/ecm/bootimg/file/340b7e5286d4/partdisk.asm#l51

> Size is rounded up to the next full sector. Further, partitions are always placed so that their start is on a head boundary (for primary and logical partitions) or so that their start is on a cylinder boundary (for extended partitions). Moreover, the size is always rounded up so that any partition ends on a cylinder boundary. (Extended partitions of type 5 must start on a cylinder boundary for MS-DOS v4 to v7 at least because their UPBs contain an amount of hidden sector within the innermost extended partition and a cylinder adjustment that is added in only after calculating the CHS from the LBA number.)

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Complete thread:

• YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - RayeR, 25.09.2025, 16:25
  • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - Laaca, 25.09.2025, 21:23
    • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - mceric, 25.09.2025, 22:27
      • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - Rugxulo, 26.09.2025, 04:57
        • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - mceric, 26.09.2025, 10:05
        • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - RayeR, 26.09.2025, 15:51
          • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - Rugxulo, 04.10.2025, 15:12
            • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - RayeR, 07.10.2025, 02:48
        • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - Khusraw, 01.10.2025, 20:03
          • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - mceric, 01.10.2025, 20:46
            • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - Khusraw, 01.10.2025, 21:06
              • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - Zyzzle, 01.10.2025, 22:09
                • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - Khusraw, 01.10.2025, 23:08
                  • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - RayeR, 02.10.2025, 08:31
                    • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - Khusraw, 02.10.2025, 10:25
                      • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - Rugxulo, 03.10.2025, 09:28
                        • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - mceric, 03.10.2025, 12:23
                          • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - rr, 03.10.2025, 14:35
                          • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - Khusraw, 04.10.2025, 19:58
                          • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - Khusraw, 04.10.2025, 20:54
                            • re: Jack Ellis' bad attitude - Rugxulo, 05.10.2025, 00:46
                              • re: Jack Ellis' bad attitude - Khusraw, 05.10.2025, 01:39
                        • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - rr, 03.10.2025, 14:37
                        • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - Khusraw, 04.10.2025, 19:10
                          • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - Rugxulo, 05.10.2025, 01:00
                            • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - Khusraw, 05.10.2025, 01:06
                              • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - rr, 05.10.2025, 10:24
                            • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - rr, 05.10.2025, 10:24
  • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - boeckmann, 26.09.2025, 10:53
    • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - ecm, 26.09.2025, 15:23
    • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - bretjohn, 26.09.2025, 23:48
      • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - boeckmann, 27.09.2025, 13:12
        • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - bretjohn, 02.10.2025, 01:05
          • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - RayeR, 02.10.2025, 18:27
            • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - bretjohn, 09.10.2025, 22:49
              • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - RayeR, 09.10.2025, 23:16
      • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - usotsuki, 03.10.2025, 19:17
  • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - RayeR, 26.09.2025, 15:55
  • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - RayeR, 30.09.2025, 16:39
    • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - boeckmann, 30.09.2025, 16:55
      • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - RayeR, 30.09.2025, 18:39
        • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - ecm, 30.09.2025, 20:07
          • YSDDT 0.1.2 (DOS Toolkit for Working with Disks & Partitions) - RayeR, 02.10.2025, 08:23