DOS ain't dead

ROM-BIOS leaves ds and es limits beyond 64 KiB (Developers)

posted by bretjohn  , Rio Rancho, NM, 31.10.2025, 01:45

> Yes, on the NEC V20 (as used by my HP 95LX) it does actually access the
> byte at offset 0000h, not 10000h, as the high byte. Not sure what Intel's
> 8086, 186, and 286 did.

And that's something I wouldn't necessarily trust that any of the modern VM's get correct, either. The only way I would believe the test was correct is if I did it on a real CPU.

I know the LOADFIX program included with early versions of DOS was supposed to resolve memory rollover issues that would crash some programs, but I don't know the exact details.

Complete thread:

• ROM-BIOS leaves ds and es limits beyond 64 KiB - ecm, 28.10.2025, 17:20 (Developers)
  • ROM-BIOS leaves ds and es limits beyond 64 KiB - Oso2k, 28.10.2025, 21:46
    • ROM-BIOS leaves ds and es limits beyond 64 KiB - ecm, 28.10.2025, 22:03
      • ROM-BIOS leaves ds and es limits beyond 64 KiB - tkchia, 06.11.2025, 17:29
        • ROM-BIOS leaves ds and es limits beyond 64 KiB - ecm, 06.11.2025, 20:13
          • ROM-BIOS leaves ds and es limits beyond 64 KiB - ecm, 06.11.2025, 20:23
            • ROM-BIOS leaves ds and es limits beyond 64 KiB - tkchia, 06.11.2025, 23:07
  • ROM-BIOS leaves ds and es limits beyond 64 KiB - bretjohn, 30.10.2025, 16:49
    • ROM-BIOS leaves ds and es limits beyond 64 KiB - ecm, 30.10.2025, 18:49
      • ROM-BIOS leaves ds and es limits beyond 64 KiB - bretjohn, 31.10.2025, 01:45
        • LOADFIX - ecm, 06.11.2025, 20:20