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Partitioning of 4TB HDD for legacy OSes (Users)

posted by Zyzzle, 29.04.2026, 01:39

> Now I hit the 2TB barrier of MBR.
 I'm still trying to figure out how to bypass 2 TB MBR limit! I think with 4k sectors, one should be able to access 16TB on an mbr partition, but both bios and DOS must support this. Raw 4k sector mode, not hybrid 512/4k mode. So far no one has taken this approach. I'm not sure if any BIOSes even support CSM mode / MBR mode with native 4k sectors. I know no DOS format utilities do. They all assume 512-byte sectors. Sadly. Even FreeDOS which has been updated very often doesn't support native 4k sectors on an MBR partition, booting to baremetal DOS.

And bypassing 2gb/4gb filelimit; I know we've got NTFS and exFAT readers for DOS, but all DOS programs and utilities I've tried do not read past 2gb-1 and only one or two will even read to 4gb-1 in native baremetal DOS 7.1 even on NTFS / exFAT drives.

I would indeed be great to get 16tb in DOS / MBR. RayeR's modulo error is typical of the buggy BIOSes and incompatibility we see in trying to press the limits. The partitions don't have to be bootable, just recognizable when one boots with a FAT / FAT32 usb memory stick, which is of course < 2TB and MBR.

bret, when you say your USB utilities enable GPT partition reading in DOS, this is only for USB devices, correct? You do not patch DOS to enable GPT reading of all non-bootable partitions attached to the system (including SATA / AHCI internal drives?)

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