Re: Mounting a 2gs hard drive on a MacSE/30 system7.5.3

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

Supertimer <supertimer@aol.com> wrote:

> goble@kin.on.net (David. E. Goble) wrote:
>
> >I found that ADU v1.2 will not partition this drive

In what way did it fail to partition the drive?  Did it report some kind
of error message?

> >I remembered that it was initially partitioned with ADU v1.1, so tried
> >it. ADU v1.1 repartitioned the drive, but having the GenericScsi file
> >from ADU v1.2 in the system/drive folder did not work.
>
> I suppose that means ADU v1.1 lacks the driver, unlike ADU v1.2.

Correct.  Support for setting up a Mac driver was added in 1.2, and the
Apple driver resources were added at this time.

> >I managed to connect the drive to an adaptec 1515 on a 486 running dos
> >6 and win 3.x. Where I partitioned it, used it, then reconnected to
> >the Apple2gs and the apple 2gs partitioning and file format was still
> >avialable. This is one tought HARD drive.
> 
> I think DOS FAT and IIGS/Mac partitioning systems store the
> partition data in different areas, which is why both can remain.

To some extent.  A bootable FAT hard drive will probably overwrite the
Macintosh Driver Partition Map, which lives at the beginning of physical
block 0.  It is possible to set up a hard drive which contains valid FAT
and Apple (HFS/ProDOS/etc.) partitioning, and it can even boot a Mac
and/or Apple II, but not a PC.

Repartitioning an Apple-partitioned drive on a PC will leave at least
part of the partition table intact, and may even leave a ProDOS root
directory behind, depending on the drive geometry (real or emulated).


The best example of this is the ZIP Tools disk that comes with an Iomega
Zip drive.  The disk contains both HFS and FAT partitioning and file
systems, allowing either a Mac or PC to use it as a native volume.

The key points are:

- The Mac driver partition map goes at the beginning of block 0.
- The Mac partition table starts at block 1 and continues for
  as many blocks as necessary.  Mac partitions can be set up on
  any block boundary on the drive.

- The PC primary partition map goes at the end of block 0.
- The PC does not use the rest of the first track.  PC
  partitions must start on track (or is it cylinder?) boundaries.

[The following details are less certain.  I may have the order backwards
for the Mac and PC halves.]

The rest of the ZIP Tools disk is set up as a normal FAT partition (boot
block, FAT tables, root directory, file area).  There is a large
invisible file that occupies the second half of the disk.

In the Mac partition table, the area corresponding to the first half of
the disk is marked as a reserved partition, and the area corresponding
to the second half (the invisible file in the FAT partition) is an HFS
partition.

The end result:

- a PC sees the disk as FAT disk which happens to contain a large
  invisible file.

- a Mac sees the disk as an HFS disk which happens to contain a large
  reserved partition.

(The Mac sees it as HFS in preference to FAT because HFS gets first go
at a mounted disk.  If PC Exchange looked at it first then the Mac would
see it as a FAT disk.)

The installation software has a procedure for freeing up the reserved
area, allowing the other half of the disk to be used on whichever
machine is appropriate.  On the PC, this is a simple matter of deleting
a large file.

On the Mac, it is a little more complicated.  I haven't investigated,
but I expect the reserved partition is replaced with a full size HFS
partition, and all the data is copied back to the beginning of the disk.

> What I suggest doing is low-level formatting the drive on a Mac,
> completely obliterating all partition data so you have an empty
> drive.  Then you can try ADU v1.2 with the GenEx extracted
> driver one more time.

This should be unnecessary - formatting the drive on a Mac would put a
driver onto it, but you would probably need to use ADU to set up a
ProDOS partition (which must be the first partition to allow GS/OS to
boot), which possibly means using ADU 1.2 to retain the Mac driver.

> Mac and IIGS partition data is the same, so formatting on one
> will definitely kill the other.  If you must do it on the 486, one
> thought is to fill up the drive under DOS.  Just copy a bunch
> of junk files to it until it fills up.  That should obliterate the IIGS
> ADU v1.1 partition data too.

Nope.  The phantom partition data is in an unused area for the PC's hard
drive organisation.

> Also, what kind of SCSI card do you have on the IIGS?  I've
> read that the Ramfast does not like ADU.

Must have an Apple card, since ADU 1.1 worked.

-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand