Re: Help with IIgs disk volume problem

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

Stephen McGrogan <smcgroga@pippin.Advent.COM> wrote:

> Nathan, thanks for responding.  I just checked the SCSI ID and it
> is six!  The only other items on the SCSI chain are the Apple High-Speed
> SCSI card and a CDROM drive.  The problem occurs with or without the CDROM.
> By the way, I had checked your FAQ before I asked the question but couldn't
> find anything germain.

What are the SCSI IDs of the CD-ROM drive and the SCSI card itself?

Have you tried setting the hard drive to a different SCSI ID (e.g. 5)
with the CD-ROM removed?  This should prove whether or not there is a
conflict with the SCSI card itself.

> Is it possible that when David (my son) copied the partition from
> the 6-partition over to the 1-partition disk that, if he had changed
> the ID on the new disk to 7 then (to avoid conflicts) that this could
> have caused this problem?

I would expect this to fail in exactly the same way - multiple copies of
the drive would appear on the desktop before you even got the chance to
copy the files over.

> Where is this volume table kept?

In an area of the disk which is not accessible using any standard tools
or even the standard disk I/O calls provided by the operating system.

> Can I patch it somehow?

Probably, but only with enough documentation to write your own utility
to access the partition table directly.

In any case, I don't think the partition table is the problem.

It is more likely to be a SCSI communication or ID problem.


The most likely explanation is that the hard drive is set to the same ID
as the SCSI card.  This causes the card to see the hard drive on every
other SCSI ID, so you would get seven copies of it (possibly one less if
the CD-ROM drive is connected).

A less likely explanation would be a fault in the hard drive which is
causing it to respond to every SCSI ID.

Also check your SCSI termination.  The last device on the chain should
be terminated, either internally or with a clip-on external terminator.
In addition, at least one device must be providing power for the SCSI
terminators.  The Apple SCSI cards don't do this (unless modified, and
recent HS SCSI cards had this modification as standard), and it varies a
lot between hard drive models.


I have two suggestions for trying to identify exactly what is happening.

1. While in Finder with the multiple images of the hard drive on the
desktop, use the Icon Info command on each volume.  Click on the "Where"
tag, and it will tell you the SCSI ID which the computer thinks the
volume is coming from.  (This only works with Apple SCSI cards.)

2. Get hold of the application "Chinook SCSI Utilities".  This was
originally commercial but was re-released as freeware.  I posted it to
comp.binaries.apple2 a while ago, but I don't know if it has been placed
on any of the FTP sites.

This program will list all connected SCSI devices and let you look at
exactly what is listed in the partition table (including the range of
disk blocks allocated to each partition).  This should prove whether
there are multiple partitions on the drive.  (Note that it is a ProDOS-8
application, and it only works with Apple SCSI cards.)

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