HP IPC (update)

From: Vassilis Prevelakis <vp_at_mcs.drexel.edu>
Date: Fri Apr 12 03:55:09 2002

This is the information I have managed to gather on the HP IPC:

First have a look at the definitive guide to the IPC

Apart from that, I have managed to find the following info by playing
with my IPC:

There is a ROM at the back behind a little door. This contains basically
the Unix OS (HP UX) and at least in my case Tech Basic. Tech Basic looks
surprisingly like Series 80 Basic (e.g the Basic on the HP-86 and 87)
including many ROM additions (e.g. IO ROM).

The funny connector on the back (like a small centronics connector) is
HP-IB (the HP name for IEEE-488) which is used to connect peripherals
like floppies and hard disks. The IPC talks CS/80 over HP-IB so it
supports "modern" HP-IB peripherals like the 9122 floppy drive.

The IPC also has in internal HP-IL bus (a two wire, low power version of
HP-IB) which is used to talk to the built in printer. At this stage
I haven't managed to investigate whether I can externalize this bus
and connect additional peripherals.

The built-in printer takes hp92261a print cartridges which (amazingly)
are still available from major mail order firms (e.g. www.staples.com
in the US, but I suppose you can get them in the UK as well). Since the
print cartridge contains the print head as well, it is very probable
that you can get the printer to work with little effort.

The IPC site (see URL earlier on) has a number of diskette images.
These are for double sided double density (720K) disks. I have
been unable to get any modern PC to write compatible floppies
using the standard double sided quad density drive (1.44Mb). I did
find a 720K drive on eBay and bought a pack of 720K diskettes.
Using OpenBSD on a PC I then proceeded to successfully transfer the
images to the floppies and access the data from the IPC.

BTW the IPC utilities in the IPC site (programs that can be used
to read IPC floppies on a Unix host) work only on big-endian
machines. You cannot use them on a i386.

Before trying to use the built-in floppy drive, note the following:

a) its totally non-standard. The connector is wrong and the RPM
is wrong. I believe there is no way that you can use a PC compatible
drive on that machine. So take good care of it!

b) the heads need cleaning and the loading mechanism needs lubricating.
If you haven't done this already, do NOT skip this step, you may
damage the disk heads if you try to use a drive with a sticky loading
mechanism. See later on for cleaning instructions.

c) The built-in disk notifies the OS when a new diskette is inserted
so that it is automatically mounted. This makes the built in floppy
more convenient than external devices.

Using the system:

Just power it up and you should see the unix boot messages. Finally you
see the desktop manager (PAM). You can type paths on the command line on
top or use the cursor keys to navigate the file system. If you have an
HP-HIL mouse so much the better you just point and click.

You should find the BASIC interpreter in /rom/basic. Until you get
the floppies from Peter's site, BASIC is the only way to use the machine.

        MASS STORAGE IS path
to change your working directory and
        CAT path
to list directories.

If you need documentation on Tech BASIC, I suggest you buy an HP-86/87
Owner's manual on eBay. They are close to the real thing and far more common
than IPC manuals.

For a hint on how to use external peripherals check the file
/documents/hp71_xfer on the IPC_BASIC_Bonus diskette.

As an example, here is a program that collects readings from an
HP multimeter (HP-IB device 13).

100 ! load HP-IB driver
110 MASS STORAGE IS "/dev"
120 ! on Series 80 the HP-IB card is always number 7
130 ASSIGN 7 TO "hpib"
140 ! The 13th HP-IB device is therefore 713
150 m=713
160 ! switch multimeter to remote control
170 REMOTE m
180 ! program multimeter for resistance, auto zero and trigger mode
190 OUTPUT m; "F3R1Z1T2"
200 ! initialize "previous" reading
210 v0=-1
215 DISP "Ready: press STOP to terminate program"
220 ! do while true
240 ENTER m; S$
250 ! display value only if different from earlier reading
260 IF v0<>v THEN DISP v
270 v0=v
280 GOTO 220


Drive removal:

Get a torx #10 screwdriver, almost all the screws on the IPC are
of this type so there is no point in trying to do any maintenance
without one.

The plastic diskette eject button seen from the front of the machine,
is not attached to the drive and is likely to fall off when you
remove the drive. It is best to secure it in place by covering it
with a small piece of adhesive tape. This will keep it in place
during the removal and subsequent installation of the diskette

First remove the back panel. You do NOT need to remove the system ROM
to do this, so leave it alone. The panel is held by just two screws
(probably the only screws that need a flat blade screwdriver) and hinges
on the bottom of the machine. Once the panel is removed you can see
the inside of the machine. A big PCB to the left and the floppy to the

Open the printer door (on the top of the machine) and look at the bottom
of the storage compartment next to the printer. You should see two black
screws. Remove them. Now the only screw holding the diskette assembly
is on screw on the bottom of the assembly (right on top of the PSU).
remove the connectors and the last screw. The floppy should slide out
towards you.

Looking at the the floppy assembly you see a mounting bracket and a
full height floppy. Before removing the drive from the mounting
bracket mark the orientation of the floppy drive against the bracket
with a pencil this will make reassembly easier. Remove the mounting
bracket and the metal cover of the floppy. Do not forget to remove
a black screw on the back of the floppy, otherwise you will not be
able to slide the metal cover out. You should see the loading
mechanism on the sides of the floppy. Try inserting a diskette to
see how it causes the loading tray to slide along paths on the fixed
sides of the drive. These are the only parts that need cleaning and
oiling. Use machine lubricating oil (under no circumstances should
you use stuff like WD-40). Apply one or two drops on each side and
insert/remove the floppy until it slides in and out effortlessly.

I use a cleaning floppy to clean the heads, so there is nothing more
to do at this stage other than closely inspect the READ/WRITE heads.
Hopefully they should have the obvious orientation that allows them
to come into contact with the magnetic surface of the floppy. If
this is so, then you are in luck, otherwise you lose.

Replace the cover and secure the floppy on the mounting bracket. Orient
the drive and bracket so that the two screw holes are on top and slide
the entire assembly inside the IPC. Attach the top two screws and the
bottom screw. You may need to slightly adjust the drive mounting assembly
to align the bottom screw. Replace the power and data cables and
reattack the back panel. Remove the piece of adhesive tape securing
the eject button and you are ready.


Corrections or additions are always welcome.

Received on Fri Apr 12 2002 - 03:55:09 BST

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