Notes on 9144 tapes

Installation and configuration

ioscan
lsdev

Usage

cat myfile | tcio -oe /dev/rct/c07d03  # write "myfile" to tape, put tapemark at nearest 1k boundary
tcio -i /dev/rct/c07d03 >myfile        # read  "myfile" from tape

dd   if=/dev/rct/c07d03      of=diskfile bs=32k
tcio -i /dev/rct/c07d03 | dd of=diskfile bs=32k # if plain 'dd' doesn't work

Documentations

• Hardware manual
• HP journal

Internet/Usenet snippets

The HP9144 tape drive is a CS80 device, it thinks it a disk drive.  It
requires specially formated DC-600HC tapes.  These tape are (Were?)available from
HPDirect sales.  
Imation says they still have the DC-600HC tape as a product.
The tapes come formated with a SDISC file system created.  The drive
was just used as a backup and data transfer device.  It can only
hold 67MB of data and because it looks for defective blocks at
tape load time.  It takes several min. to mount in the drive.
Also, in the tape header the is a counter as to the number of
write passes the tape has seen.  
When the counter reaches a given point the tape becomes readonly.
So, after you write your data to the tape unload it and set the
write protect on the cart. 

9144A 9145A 35401A Cartridge Tapes

There are a number of formats employing seemingly identical 1/4-inch
cartridges.  The most common are the various QIC definitions (QIC =
Quarter Inch Committee).  Sun and Apollo systems, for example, often
use QIC-24 (60 Mb).  Traditional HP drives do not use the QIC format,
but rather one invented by 3M some five years before QIC.  It is
called HCD format and first appeared on the HP 7908A disk drive as an
integrated disk/tape storage device. Internally, HP called this tape
mechanism "Linus" which later appeared on the 7911, 7912 and 7914
disk drives.

The format was quite popular as an inexpensive (at that time) method
to store up to 67 megabytes of data.  As a result, HP designed the
external version called the 9144 (also known as the Buffalo), the
35401A changer and finally, the 9145 which doubled the track density
and resultant storage capacity.

Inserting an HP cartridge in a QIC drive leads at the very least to
frustration, and potentially to permanent damage to the HP tape.

Attempting to use a QIC tape in an HP HCD drive results in:

  0. Tape rejected.
  1. Possible tape unspool after repeated attempts.

Attempting to use an HCD tape in a QIC drive results in:

  1. No data exchanged.
  2. An apparently damaged tape (rewind scenario).
  3. A probably destroyed tape if a manual reposition.
  4. A definitely destroyed tape (write scenario).

Cartridge Tape Specification Overview:

+====================+=========================+====================+
| Characteristic     | HCD Cartridge Tape      | QIC Cartridge Tape |
|====================+=========================+====================|
| Approx. Incep. date| 1980                    | 1985               |
|--------------------+-------------------------+--------------------|
| Mechanical form    | 3M DC600                | 3M DC600           |
|   factor           |                         |                    |
| Merchandising name | <none, really>          | QIC-24 or QIC-120  |
|--------------------+-------------------------+--------------------|
| Typical supplier   | HP (for HP customers)   | any discounter     |
|--------------------+-------------------------+--------------------|
| Generic designation| DC600HC, DC615HC,       | DC600A, DC615A     |
|                    |   DC600XTD, DC615XTD    |                    |
|--------------------+-------------------------+--------------------|
| Tape pre-format    | Full-track 3M HCD-75    | <none>             |
|                    |   or modified HCD-134   |                    |
| Data format        | MFM                     | NRZI               |
|--------------------+-------------------------+--------------------|
| EOT/BOT            | Delimited by pre-format | Optical tape sense |
|                    |                         | holes              |
| Rewind position    | Right spool empty.      | Left spool empty.  |
|--------------------+-------------------------+--------------------|
| Capacity           | 67 or 134 Mbytes        | 60 or 120 Mbytes   |
| Number of tracks   | 16 or 32                | 9 or 15            |
|--------------------+-------------------------+--------------------|
| Access types       | Random (re-writeable)   | Serial only        |
|                    |   or serial             |                    |
| Average seek (60M) | 2 minutes               | 20 minutes         |
|--------------------+-------------------------+--------------------|
| Error control      | Read-while-write        | Read-while-write   |
|                    |   plus ECC              | only               |
+====================+=========================+====================+

As you can see, HCD has some advantages.  Errors missed by
read-after-write may still be corrected by ECC when read later.  Tapes
may be "certified" and re-certified by end users, sparing bad blocks.
The random-access capability allows software to treat the tape like a
*very* slow disk drive.  Disk-image cartridge tape backups are
mountable as read/write volumes, and may be safely written upon.

Random access is faster, because the location of every record can be
calculated, due to the pre-formatting or fixed record length. Seeking
to a specific record involves moving the head to the right track and
shifting the tape to the right spot--implemented completely in the
hardware.

HCD and QIC cartridges are mechanically identical.  An HCD cartridge
will fit in a QIC drive, and vice-versa.

So what is the problem?

 * HCD tapes are preformatted by 3M or a 3M licensee.  A full-track
   factory write head lays down fixed physical records on the tape.
   No HCD drive ever writes on these record headers (called "keys");
   only in between them.  HP "format" and/or "mediainit" user
   processes merely "certify", performing read/write tests, sparing
   bad blocks and updating logs.

   The read/write heads in the drives are either 1/16- or 1/32-track.
   Keys, being full-track, cannot be re-written in the field.

 * The keys also do not extend to the physical BOT/EOT sense holes
   in the tape.  When the first HP drives were developed in the early
   80s, optical sensing was deemed too unreliable, so all HP drives
   use boundary keys to denote BOT/EOT.  (QIC tapes are more like
   traditional 1/2-inch 9-track media.  The tapes have no
   pre-formatting, so QIC drives MUST rely on the sense holes for
   BOT/EOT.)

 * If you put a QIC tape (blank or written) in an HP HCD drive, the
   HP drive will search "uptape" (wrong way past EOT on QIC) for the
   nearest key, fail to find one, time-out, buzz, release (unload) the
   tape and illuminate the FAULT indicator.  No data lost, but no data
   is read or written either.  Repeated attempts risk unwinding the
   tape from one of the reels.

 * If the you put an HCD tape in a QIC drive, the drive will
   "rewind" it (to the wrong end of the tape by HP conventions) and
   OUTSIDE the keys region.

   Suppose the tape is removed from the QIC drive and re-inserted in
   an HP drive.  The HP drive, as in the preceding example, will
   search "uptape" for a key (again, in the wrong direction due to the
   QIC rewind), not find a key in a reasonable time, and reject the
   tape for fear of unwinding if the search continues.  It will
   buzz, release and FAULT.  Repeated attempts risk a tape spill.

   The tape may be MANUALLY wound, in the COUNTER-INTUITIVE direction,
   to reposition it inside the keys.  If re-inserted in the HP drive,
   it will properly load (after adding an extra minute to the load
   time because it was rewound to the wrong end).

   I say "counter-intuitive" because tape motion inside the cartridge
   is in the OPPOSITE direction from drive wheel motion, and the
   tensioning band makes it difficult to assess which way the tape is
   supposed to spool.  Now, also please note that in the construction
   of DC600 media, the tape ends are *NOT* affixed to the reels...

 * Given a mis-positioned cartridge, should someone manually wind in
   the intuitive {i.e. incorrect} direction, or risk repeated access
   attempts, the tape unspools.  Disassembly and re-spooling of DC600
   tapes is a nightmare for the inexperienced.

 * If, on the other hand, the HCD tape was left in the QIC drive,
   two more scenarios obtain.  The QIC drive has no clue that this is
   an HCD tape.

   1. The HCD data structures just look like noise.  In the above
      table, you will notice that the track count is different which
      means the head is a different size and will not align with the
      QIC format.Any attempt to read an HCD tape simply fails or
      returns garbage data.  If the tape is removed after a read
      attempt, the rewind scenario above prevails.

   2. A QIC drive will happily WRITE on an HCD tape.  This destroys
      both existing data AND the HCD preformatting keys.  If the
      preformatting is ever lost, the tape can NEVER be used in an HCD
      drive again.  (This problem can also happen subsequent to
      degaussing an HCD tape.)

      What happens back at the HP drive?  Apart from the
      rewind/time-out problem, as soon as the HP drive detects a
      trashed key, it will FAULT and reject the tape.  Only 3M can
      (re)format an HCD tape, and I doubt that they offer such a
      service.

If you have a tape labelled DC6xxHC, DC6xxXTD or with the [(hp)] logo
on it, don't insert it in a tape drive not known to be HP-compatible.
Most people will want to use the cartridge tapes to exchange data
between systems...the choices are limited to 1/2" magtape and DDS or
4mm DAT-style tapes as well as LAN, X.25 and modems.