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On Tue, Mar 12, 2002 at 12:10:28PM -0500, Todd Vierling wrote:
>=20
> ** amiga, amigappc **
>=20
> RDB ("Rigid Disk Block") structure first block can exist anywhere in
> 512-byte blocks 0-15.  (Note that some, but not all, Amiga boot ROMs allow
> for the RDB to exist in blocks 0-63.)

but any specification I've seen does not demand more then 16 blocks, so you
can't rely on this.

However, this is in terms of block count, where block is what is on the
disk. For 2-kByte MODs, this would be a range of 32 kBytes.

> Use of this sector starts at byte 0, length 220.  Magic word `RDSK' at by=
te
> 0 to identify it.  Checksum has variable length, so can be made to contain
> only the RDB.  (sys/arch/amiga/include/disklabel.h:struct rdblock)

every RDB block type is checksummed stand-alone. The variable length is
to indicate what length of it is actually used... I think the basic types
fit into 256 bytes, but LSEG blocks (and possibly bad block lists) can use
more than that.
>
> This structure contains a (start,count) tuple of contiguous blocks anywhe=
re
> on the disk that contain partition entries, bad block entries, and AmigaOS
> filesystem drivers (one descriptor per block).  NetBSD partitions have
> special Amiga 32-bit type IDs to provide the NetBSD fake disklabel info.

only "special" in the sense that they indicate NetBSD partitions.

> Bootblock code is loaded from the first N blocks of the boot filesystem
> partition (defined by the partition entry descriptor).


> NetBSD does not use a BSD disklabel on RDB disks; the partition map is
> read-only in this case.  (A BSD disklabel can be stored on non-RDB disks.)
>=20
> ** amiga (loadbsd method) **
>=20
> RDB exists as above, but the bootable flag is unset on NetBSD partitions.

or the NetBSD partition has a lower priority than the AmigaOS partition.

> AmigaOS boots first.  "loadbsd" is then used to load and boot the kernel.

Regards,
	Ignatios

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