[Coco] Multiple HDB-DOS 256 drive partitions Software Wanted

[Robert Gault]

Brett Gordon wrote:
> It's Cool that people are taking interest in Partitioning for the coco.
> Obviously as the CoCoBoot guy, I'm very interested in this.  I've been
> moaning and groaning about it via IRC and list for a while.  Keep in mind
> we might have more that 2 types of file systems for the coco ( RBF and
> RSDOS ) ,  Now that we have open source HDB-DOS and Nitros  is there a way
> we can all create a real partition table ?   Treating a volume as a linked
> list of filesystems only lends itself to 1 or 2 filesystem types.  Here are
> my argument for a partition table:
>
> * Arrays are slightly easier to iterate through
> * multiple ( more than 2) filesystem types can be supported
> * The FS types can be indicated in the table rather than grokking
> filesystems.   With a linked-list,  systems including HDB, Nitros, CoCoBoot
> have to do this grokking to figure out what a partition is.
>
>

The partitions referred to in this thread should not be confused with PC hard 
drive partitions. HDBDOS and RGBDOS split a hard drive into two sections based 
on three bytes in the Disk ROM. These bytes, $D938-$D93A, give the address of 
the first Disk Basic sector on the hard drive. There is no indication on the 
drive itself that sectors differ on either side of this "border".

The sectors can be any size in bytes and that is a function of the hard drive, 
hardware or emulation. Regardless of the sector sizes, Disk Basic can only use 
256 bytes per sector. The rest will be wasted unless unless the ROM is modified 
to work with pseudo sectors. OS-9 can do this but there is not enough room in 
the Disk ROM to compensate for alternate size sectors. Only the first 256 bytes 
will be used.

All emulators use 256-byte sectors.