Real tape drive densities

[Chuck Guzis]

On 02/14/2016 06:13 PM, Jay Jaeger wrote:

>
> Maybe some yahoo decided to write over the first file of that SVR4 tape
> at higher density so as not to clobber the files after it.  Smart, so as
> not to clobber the other stuff, but crazy.  Or it may have been just a
> case of writing that first file, with no double-EOF EOT on it.
>
> Or maybe someone wrote the first file and then went "OH SH*T that was a
> DISTRO TAPE wasn't it..."  ;)
>
> Anyway, I doubt AT&T would have written the tape that way intentionally.

Well, the tape bears an AT&T label.  The tape itself comes from UCB at 
about the same time that "ernie" was in use, so VAX or PDP11.  It could 
be a copy of an AT&T distro tape with the duplicate label attached. 
It's a 2,222,000 byte cpio file that starts out with:

#       THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF AT&T
#       The copyright notice above does not evidence any
#       actual or intended publication of such source code.

#ident  "@(#)mk::mk     1.10"
#
#       Shell script for rebuilding the UNIX System
#
trap "exit 1" 1 2 3 15
if [ "$ROOT" = "" ]
then
         PATH=/bin:/etc:/usr/bin; export PATH
fi

That's the 6250 GCR file; the 1600 PE file that follows is a 37,432,320 
byte cpio file that starts out in exactly the same way.  The 2MB file 
was probably an "osh*t" file as it terminates prematurely at 
"usr/src/cmd/bnu/bnu.mk".

I read it on my Fuji 2444 (Pertec interface).  None of my SCSI drives 
could handle the mixed density.

Just curious--

How many "smart" drives can handle multiple load points?  Before the day 
of autothreading drives, it was convenient to have a "universal 
deadstart" tape to carry along, with various operating systems on it. 
Just keep hitting the "load" button until you get to the one you want, 
then push the button.

--Chuck