Date: Mon, 3 May 1999 12:29:16 -0400
From: Tim Shoppa <SHOPPA@trailing-edge.com>
To: PUPS@minnie.cs.adfa.edu.au
Message-Id: <990503122916.20c010f3@trailing-edge.com>
Subject: Re: SunOS 0.4 tape
Sender: owner-pups@minnie.cs.adfa.edu.au
Precedence: bulk

>When sorting through old things in the machine room here recently,
>Job Bogan came across an early QIC tape of SunOS.  The label reads:
>
>    Sun UNIX 4.2* Software Release 0.4
>          (*Berkeley Beta Release)
>    1/4" Boot Tape 1 of 2 700-0585-01
>    copyright (c) 1983 Sun Microsystems
>
>Unfortunately, when I attempted to read the tape, all I got was a
>tar file of a Fortran program dating from 1989.

So presumably someone decided to re-use this tape - and we hope they
didn't reformat the tape first.

>  It didn't get very
>far into the tape, though, so parts of the original software may
>still be present -- but I don't know how to get past the end-of-tape
>mark to get at them.  Any ideas?

QIC tape formats have physical sectors that the controller (in your
case, most likely the SCSI controller that interfaces the drive to
your SCSI bus) presents to the rest of the system as a series of
logical tape records and tape marks.  You can't get past the logical
end-of-tape because the SCSI controller (not host adapter!) "knows"
there's nothing past the logical end-of-tape.  If you bypass this
by going straight to the physical sectors, you can read the data
following logical end-of-tape, assuming that the cartridge was
never reformatted.  Most SCSI QIC tape controllers will let you
get at the physical sectors, but this is rarely supported by the OS
and isn't always consistent from model to model and manufacturer
to manufacturer.

QIC tape standards are pretty well documented at http://www.qic.org/.
For details on how your SCSI QIC drive can be forced to access
physical sectors, it's best to go straight to the drive manufacturer's
technical manuals.

-- 
 Tim Shoppa                        Email: shoppa@trailing-edge.com
 Trailing Edge Technology          WWW:   http://www.trailing-edge.com/
 7328 Bradley Blvd		   Voice: 301-767-5917
 Bethesda, MD, USA 20817           Fax:   301-767-5927