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Book8088's CF2IDE stumps Freedos boot (Users)

posted by roytam, 04.02.2024, 05:52

> > > XT-class BIOSes don't usually support LBA, so the DOS kernel has to
> use
> > CHS
> > > to access the sectors on the disk.
> > >
> > > Many DOS implementations (probably at least FreeDOS and MS-DOS, not
> > sure)
> > > detect the disk geometry from the information in the FAT boot sector,
> so
> > > you cannot just write any random filesystem image to the SD card with
> > > Linux's dd command and expect it to work properly.
> > >
> > > When creating the filesystem you need to use the same geometry that
> the
> > > Book8088's BIOS uses.
> > >
> > > At least MS-DOS and FreeDOS also require that the disk is partitioned.
> > The
> > > starting sectors of the partitions in the partition table also need to
> > be
> > > compatible with the actual geometry.
> >
> > you can test it with 86box, with 8088 machine with XT-IDE and a disk
> image
> > with CHS=1006/16/63, partitioned and formatted with DOS 3.31, and boot
> with
> > FreeDOS 2043-86 kernel (F16/F32 doesn't matter) and you can get same
> > error:
> > [image]
> > (I even tried latest snapshot uploaded in github, but it makes no
> > difference)
>
> There may also be something wrong with FreeDOS. I noticed that for some
> reason ST-DOS's partition mounter can parse logical partitions that are
> created with MS-DOS 6.22, but it has problems parsing logical partitions
> that are created with FreeDOS. FreeDOS is probably not fully following the
> specification of the MS-DOS partition table. FreeDOS doesn't have problems
> parsing partition tables that are created with its own FDISK though.
>
> FreeDOS is clearly doing something differently than MS-DOS, but I haven't
> investigated what exactly is the difference.
>
> Different versions of MS-DOS also create different partition tables and
> parse them differently, and they may not be 100% compatible with each
> other. MS-DOS 3.31 is a relatively old version, and FreeDOS only aims to be
> compatible with MS-DOS 6.22.
>
> I recommend at least creating the partition tables and filesystems with the
> same operating system that is going to use them.
same HD image booted with QEMU and DOS 6.22 shows no problem:
[image]
[image]

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