Re: :( 12 Partition Limit!?!?!??? :(

[dempson@atlantis.actrix.gen.nz (David Empson)]

In article <C070496234857.5760@darkcastle.ecore.fnet.org>,
Dark_Dude <Dark_Dude@darkcastle.ecore.fnet.org> wrote:
> 
> In Article <31DB7CDD.15CC@rmci.net>,
> <Mikeal@rmci.net> wrote:
> 
> >Why can't someone redo the SCSI card for the Apple //'s in such a
> >way that it will use the fullness of some of these new drives, 720 meg, 1
> >gig, 1.5 gig, etc. And be able to go beyond the 12 partitions limit.
> 
> I remember Jan Maes telling me that you could have more than 14 partitions,
> 110 max. but they were the sum of several scsi devices. I don't recall how
> that worked...

The Apple High-Speed SCSI card has an internal limit of 110 partitions
(I thought it was 111) in total, spread over all connected hard drives.

Through the ProDOS block driver, you can only access the first two, or
the first four if the SCSI card is installed in slot 5.  (This is how
ProDOS-8 1.9 and earlier use the card).

If you use the SmartPort driver, you can access all partitions.
ProDOS-8 2.0 and later use this method to access the partitions after
the first two (or four), but there is still the 14 volume limit imposed
by ProDOS's unit numbering and internal tables (13 once you exclude
/RAM, minus two for each other slot which contains a disk controller
or equivalent).

The original Apple SCSI card has an internal limit of 7 partitions, so
you will never be able to access more than that from ProDOS-8, short
of bypassing the firmware and doing direct SCSI calls (which is not
easy with this card).

Note that these limits do not apply to GS/OS, which accesses the
hardware directly from its own drivers.

I don't know what internal limit the RamFast has on the number of
partitions.


The best method of handling a large hard drive would be for someone to
write a utility that patches ProDOS's internal tables to select between
arbitrary 32MB partitions on a large hard drive (or drives).  You
could then remap any ProDOS partition to any unused ProDOS unit number
(probably still excluding real devices, to avoid confusing software
that tries to work out what device it is talking to).
-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand