DOS ain't dead

Adding large disk support to INT13h (Users)

posted by boeckmann, Aachen, Germany, 02.04.2024, 19:31

> > my Pentium MMX motherboard INT13h functions do not support disk sizes
> > larger than 8.4GB, but the chipset does. Is there any open source
> solution
> > to add large disk support that does not require me putting in another
> > controller or burning an XT-IDE rom?
>
> I think you want an open source alternative to ontrack or ezdrive? You
> could start with XT-IDE and write a little loader to put it in RAM. The
> closed source tools mentioned are similar, they come with a MBR to load
> them in RAM, often allocated via manipulation of 40:13 memory size.
>
> They typically even hide themselves by shifting the entire disk contents,
> so the initial part where the "driver" resides is only visible until the
> "driver" gets loaded. As there usually is plenty of space in the first
> track, I disliked that method. If you write some open source xt-ide loader,
> avoid such shift tricks if possible. You could even load it "metakern
> style" from a DOS boot sector and then chain load the normal DOS kernel
> after the "driver".
>
> Note that most older IDE controllers are not smart, so they have no opinion
> about CHS versus LBA. Only the different PIO, DMA and UDMA styles
> available are likely to actually depend on your hardware.

Hi Eric,

as far as I know these disk utilities (they seem to be called dynamic drive overlay) increased the maximum disk size from 503 MB to 8.4GB. Probably one or another of them also supports larger disk sizes. Interesting that there does not seem to be an open source equivalent to these tools. Perhaps too exotic

I will try the "XT-IDE loaded from floppy" route, and perhaps the "XT-IDE -> original boot sector chainloading" in another step.

I am still not sure what the implications are of stealing a few KB from conventional memory by decreasing 0x13 of the BIOS data area.

Complete thread:

• Adding large disk support to INT13h - boeckmann, 01.04.2024, 11:54
  • Adding large disk support to INT13h - RayeR, 01.04.2024, 15:31
    • Adding large disk support to INT13h - boeckmann, 01.04.2024, 18:44
  • Adding large disk support to INT13h - bretjohn, 01.04.2024, 17:28
    • Adding large disk support to INT13h - boeckmann, 01.04.2024, 18:41
      • Adding large disk support to INT13h - bretjohn, 02.04.2024, 16:54
        • Adding large disk support to INT13h - boeckmann, 02.04.2024, 19:23
          • Adding large disk support to INT13h - bretjohn, 04.04.2024, 19:33
            • Adding large disk support to INT13h - boeckmann, 04.04.2024, 23:09
              • Adding large disk support to INT13h - Laaca, 05.04.2024, 06:23
                • Adding large disk support to INT13h - boeckmann, 07.04.2024, 20:21
  • Adding large disk support to INT13h - mceric, 01.04.2024, 22:25
    • Adding large disk support to INT13h - boeckmann, 02.04.2024, 19:31
      • Adding large disk support to INT13h - mceric, 02.04.2024, 20:57
      • Adding large disk support to INT13h - tom, 02.04.2024, 23:16
        • Adding large disk support to INT13h - boeckmann, 04.04.2024, 23:09
        • Adding large disk support to INT13h - Japheth, 05.04.2024, 02:39
      • Adding large disk support to INT13h - ecm, 14.04.2024, 19:19