DOS ain't dead

failed with hybrid MBR under Windows (Users)

posted by bretjohn  , Rio Rancho, NM, 07.05.2026, 22:36
(edited by bretjohn on 07.05.2026, 23:45)

This site contains a little bit of info on the various partition types that can be in an MBR:

https://thestarman.pcministry.com/asm/mbr/PartTypes.htm

EEh (GPT Protective MBR) is the "standard" GPT, and there is also EFh (EFI/UEFI System Partition) which seems to only be used by Windows and I'm guessing somehow interacts with the EEh.

Officially, EEh is supposed to be a single partition that encompasses the _entire_ drive, or at least the first part of the drive that the MBR can handle (~2TB if the sector sizes are 512 bytes). The other entries are supposed to be 0. The GPT is _supposed to be_ the only place that contains real partition information. Various vendors will handle an "incorrect" protective MBR's differently, as you have discovered. A hybrid MBR is _not_ universal and is _almost guaranteed_ to cause you grief at some point. Even in my USB disk drivers, when I see the EEh I do a little bit of checking (though far from complete) to see if it really looks like a valid protective MBR, and use the GPT instead of the MBR. If I see the EEh and it doesn't look like a valid protective MBR, I assume it's a regular MBR and the EEh is a mistake or something weird is going on and it's not really GPT.

Complete thread:

• Partitioning of 4TB HDD for legacy OSes - RayeR, 27.04.2026, 22:45 (Users)
  • Partitioning of 4TB HDD for legacy OSes - mceric, 28.04.2026, 01:35
    • Partitioning of 4TB HDD for legacy OSes - bretjohn, 28.04.2026, 03:04
      • Partitioning of 4TB HDD for legacy OSes - Laaca, 28.04.2026, 05:08
        • Partitioning of 4TB HDD for legacy OSes - RayeR, 28.04.2026, 17:28
          • Partitioning of 4TB HDD for legacy OSes - Rugxulo, 29.04.2026, 05:23
            • Partitioning of 4TB HDD for legacy OSes - RayeR, 29.04.2026, 20:09
        • Partitioning of 4TB HDD for legacy OSes - bretjohn, 28.04.2026, 17:30
          • Partitioning of 4TB HDD for legacy OSes - Laaca, 28.04.2026, 18:31
            • Partitioning of 4TB HDD for legacy OSes - RayeR, 28.04.2026, 20:31
    • Partitioning of 4TB HDD for legacy OSes - RayeR, 28.04.2026, 17:21
  • Partitioning of 4TB HDD for legacy OSes - Zyzzle, 29.04.2026, 01:39
    • Partitioning of 4TB HDD for legacy OSes - bretjohn, 29.04.2026, 03:39
    • some TSR/patch to modify BIOS/EDD? - RayeR, 29.04.2026, 20:20
      • some TSR/patch to modify BIOS/EDD? - ecm, 29.04.2026, 20:56
        • some TSR/patch to modify BIOS/EDD? - RayeR, 30.04.2026, 17:31
          • some TSR/patch to modify BIOS/EDD? - ecm, 30.04.2026, 20:06
          • some TSR/patch to modify BIOS/EDD? - Laaca, 01.05.2026, 12:24
          • some TSR/patch to modify BIOS/EDD? - RayeR, 04.05.2026, 17:48
            • failed with hybrid MBR under Windows - RayeR, 07.05.2026, 15:40
              • failed with hybrid MBR under Windows - bretjohn, 07.05.2026, 22:36
                • failed with hybrid MBR under Windows - RayeR, 09.05.2026, 18:16
                  • failed with hybrid MBR under Windows - RayeR, 11.05.2026, 07:47
                    • New Idea how to beak 2TB on WinXP-32 - RayeR, 23.05.2026, 13:51