Re: Apple 2 SCSI HD format compatability

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

Bryan aka R.I.P. <gmezero@gz.bomb.com> wrote:

> soo... I was wondering. If I format a SCSI HD under ProDOS on my
> Enhanced //e... say, make a 20mb partition. Could I read the partition
> on any other kinds of computers? Mac? PC? ???

As long as you partitioned the drive (rather than creating a single 20MB
volume), then the Mac can theoretically recognise the drive, because the
Mac and Apple II use the same partitioning scheme.

There are some catches, however.

1. The Mac requires a device driver, stored on the hard drive (in its
own partition) to be able to support a SCSI hard drive.  This is usually
placed on the drive by the Mac-based formatting/partitioning software.

If you format/partition the drive on a IIe, this driver will not be
present, so the drive won't be recognised by the Mac.

It is possible to format and partition a drive on the IIgs and have it
recognised by the Mac, because the GS/OS partitioning software (Advanced
Disk Utility) is able to place a Mac driver onto Apple-branded drives
(and can be patched to handle most drives).

Another option is to format and partition the drive with appropriate
software on the Mac, then erase one or more partitions on the Apple II
for use with the ProDOS file system.

2. Assuming you have a Mac driver on the drive, the Mac needs the right
software installed to handle the ProDOS file system (installed by
default for the last few years).  It is also possible to use the HFS
file system to share data between the Mac and IIgs, but there is only
very limited support for HFS on the IIe (A2FX and HFSLink, and I don't
know if either of them can handle a hard drive).


As for the PC: I've never dealt with SCSI hard drives on a PC, so I'm
not entirely clear on how they compare with traditional ST-506 or IDE
hard drives as far as the partitioning goes.  I expect they emulate the
cylinder arrangement and hence use the same partitioning scheme.  This
is different from the Apple II and Mac partitioning scheme, so it is
usually the case that a PC would not recognise the partitioning of an
Apple II or Mac hard drive.  I imagine there is software which allows
you to mount a Mac hard drive on a PC, and in theory this could also
support Apple II hard drives, as long as it can handle the ProDOS file
system.