## Building an ITS from scratch on the Supnik PDP-10 simulator

         $Revision: 1.8 $
         $Date: 2003/07/20 19:38:11 $

Copyright © 2001,2003 Mirian Crzig Lennox
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation.

### Getting Started

First of all, it is assumed that you have read and understand `AI: KSHACK; BUILD DOC`. For your convenience, a copy is available here. This file should be considered a companion to that document, not a replacement.

ITS supports four different disk types: the RM03, the RM80, the RP06 and the RP07. Although these disk types are very different at the hardware level, from the simulator's point of view they differ only in capacity and geometry. This document uses the RP06 as an example; however, the procedure is similar for any of the other three disk types.

Materials you will need to install ITS:

- A working `pdp10` executable from the SIMH simulator. This document assumes that SIMH V3.0 is being used.
- The RP06-based Salvager boot tape image `salv.rp06.tape`.
- The RP06-based `DSKDMP` boot tape image `dskdmp.rp06.tape`.
- A `MINSYS` tape image. This is a DUMPER tape containing a minimal ITS bootstrap system. The contents of these may vary, however a usable one is available here: `minsys.tape`.

### Conventions used in this document

Throughout this document, sample output from the simulator is shown in `typewriter font`. Keyboard input required to be typed by the user is shown in `bold typewriter font`.

The symbol `«` is used to indicate where a carriage return should be typed; this is necessary because ITS programs are not consistent about requiring a carriage return or not, and in cases where a carriage return is not expected by the program, the carriage return will be taken as input to the following query, which is likely to be incorrect.

The constructs `ESC-g` and `^C`, where `g` and `C` represent any letter of the alphabet, have their usual meanings: `ESC-g` means to type the Escape key and then the letter `g` and `^C` means to hold down the Control key and type the letter `C`.

### Configuring the Simulator

Create a file named `init` containing the following:

    set cpu its
    set tim y2k
    at tu0 minsys.tape
    at tu1 salv.rp06.tape
    at tu2 dskdmp.rp06.tape
    set rp0 rp06
    at rp0 rp0.dsk

This is the configuration file that the PDP-10 simulator will use; it contains commands which will be executed when `pdp10` starts. The various lines are explained below:

- `set cpu its`
  This tells SIMH to simulate ITS IO and paging microcode, which differs significantly from the standard DEC microcode.
- `set tim y2k`
  This tells the simulator that you are using a Y2K-aware operating system (which ITS is), so it can report the time correctly for the 21st century.
- `at tu0 minsys.tape`
  Mount the `MINSYS` tape on tape unit 0.
- `at tu1 salv.rp06.tape`
  Mount the RP06 version of Salvager boot tape on tape unit 1.
- `at tu2 dskdmp.rp06.tape`
  Mount the RP06 version of `DSKDMP` boot tape on tape unit 2.
- `set rp0 rp06`
  Tell disk unit 0 that it will be simulating an RP06.
- `at rp0 rp0.dsk`
  This mounts the simulated disk image `rp0.dsk` on disk unit 0. However, this image does not yet exist; it will be created by the simulator.

### Formatting the disk image

Start the simulator with the configuration file you just made:

    $ pdp10 init«

    PDP-10 simulator V3.0-0
    RP: creating new file
    sim>

The `sim>` is the front-end console prompt. Typing `help` to it gives a list and short description of the commands it understands. To prepare the initial disk image, you need to boot the Salvager tape:

    sim> b tu1«
    ITS MTBOOT.176

The Salvager doesn't have a prompt or any command-line interface at all; at this point you are talking to Exec-`DDT`. In order to call Salvager functions, you need to use `DDT` to call them. Note that `$` is the character printed by `DDT` when the Escape key is typed, so when you see `$`, type the Escape key, not a dollar sign. Also, `DDT` prints a single quote `'` whenever it recognizes a symbol for the first time; when you see a `'` in the sample output below, you are not expected to type this character.

First, you need to “mark” (format) the disk, so type

    MARK$G'
    Format pack on unit #0
    Are you sure you want to format pack on drive # 0 (Y or N) y
    Pack no?0«
    Pack 0., Drive #0 is serial #17.
    Begin formatting 815. cylinders....Hardware formatting complete.
    Verify pack? (Y or N) n«

Be sure you answer in the negative when asked to verify the pack. For technical reasons beyond the scope of this document, verification does not work (and isn't necessary anyway, since our simulated disk won't have any hardware errors).

You will then be asked for some filesystem parameters:

    Swapping Alloc? 3000«
    Pack #0.  ID?foobar«

    DDT

Of course, you can choose any name of six characters or less for the Pack ID in place of “foobar” above.

The disk is now formatted, and the Salvager returns you to `DDT`.

Important note: If you are using SIMH V3.0-0 only, you will need to reboot the Salvager tape at this point. This is because of a bug in the “read header” function in the RP device. The bug is fixed in V3.0-1 and later, so only users of V3.0-0 need to perform this step:

    ^E

    Simulation stopped, PC: 773131 (POPJ 1,0)
    sim> b tu1«
    ITS MTBOOT.176

### Loading `MINSYS`

Now that you have a formatted disk, you need to load the minimal bootstrap ITS, called `MINSYS`. This is accomplished with the `TRAN` utility in Salvager:

    TRAN$G

    onto unit #0
    Copy from unit #5 onto unit #0, OK (Y or N) y

“Unit #5” is just the Salvager's name for the tape drive. It has no real significance. Once you type y, a flood of filenames should scroll by as the `MINSYS` files are loaded. Each filename should be followed by `OK` to show that the file loaded without error. (The elipsis (`...`) indicates where the sample output has been trimmed for brevity.) When all the files have been transferred, `EOT` will be printed, followed by the `DDT` prompt:

    Tape #0
    .;@ DDT OK

    .;ITS RM03 OK

    .;ITS RM80 OK

    .;ITS RP06 OK

    .;ITS RP07 OK

    .;SALV RM03 OK

    .;SALV RM80 OK

    .;SALV RP06 OK

    ...

    SYS2;TS FTP OK

    DEVICE;TCP SYN025 OK

    SYS;SYSTEM MAIL OK

    EOT

    DDT

### Building the ITS monitor image

Now it is time to halt the system and boot from the other boot tape, `DSKDMP`. This is a standalone utility that allows us to build an executable image out of pieces and dump the results into a single image. To halt the simulator and return to the front-end console, type `^E` (control-E). Then, boot from tape unit 2, and when the `MTBOOT` prompt comes up, start `DSKDMP` by typing `ESC-g`

    ^E

    Simulation stopped, PC: 773035 (JRST 0,773034)
    sim> b tu2«
    ITS MTBOOT.176
    $G

    DSKDMP

`DSKDMP` knows how to read an ITS filesystem and load files into memory (and write files back to disk). By default, filenames are expected to be in the `.` directory and to have `@` as the first filename (the convention for standalone executable files).

Load a copy of standalone (Exec) `DDT` from `.; @ DDT` like so:

    l$ddt«

Then load a copy of the ITS binary which is appropriate for the disk type you are using (`.; ITS RP06` in our case). We use the `T` command which gives the file's symbols to `DDT`, and then starts `DDT`:

    t$its rp06«

Now you are back in `DDT`, but you still need to go back to `DSKDMP`, so type `ESC-u`.

    $U
    DSKDMP

Now merge in a copy of the Salvager binary appropriate for your disk type (RP06):

    m$salv rp06«

And finally, dump the whole thing out as `.; @ ITS` as so:

    d$its«

You can list the `.` directory with the `F` command:

    f$
    #00 @      ITS
    #00 RAM    RAM
    #00 BT     RP07
    #00 BT     RP06
    #00 BT     RM80
    #00 BT     RM03
    #00 DSKDMP RP07
    #00 DSKDMP RP06
    #00 DSKDMP RM80
    #00 DSKDMP RM03
    #00 SALV   RP07
    #00 SALV   RP06
    #00 SALV   RM80
    #00 SALV   RM03
    #00 ITS    RP07
    #00 ITS    RP06
    #00 ITS    RM80
    #00 ITS    RM03
    #00 @      DDT

You should notice that the first filename in the listing is now `@ ITS` which is the file you just built.

### Booting the dumped ITS

Now the big moment: time to boot that ITS image. First load it by typing its name, and then use `ESC-g` to start it:

    its«
    $G

    Salvager 255

If all goes well, you should soon start seeing bootup messages from ITS:

    DB ITS 1633 IN OPERATION
    DB ITS 1633 SYSTEM JOB USING THIS CONSOLE.
    THE KS-10 CLOCK HAS BEEN RESET, IF THE TIME CANNOT
    BE DETERMINED FROM THE NETWORK, YOU MAY HAVE TO :PDSET
    YEAR, PDTIME OFFSET, NOT ON DISK.
    PLEASE SETLOC APPROPRIATELY.
    LOGIN  TARAKA 0
    TOP LEVEL INTERRUPT 40 DETACHED JOB # 2, USR:TARAKA DRAGON

Now ITS is in full timesharing mode and waiting for you to log in on the console. Type `^Z` to get its attention:

    ^Z
    DB ITS.1633. DDT.1546.
    TTY 0
    You're all alone, Fair share = 99%

    (ITS does not know the date, so messages cannot be reviewed right now.)

### Setting the correct time with `PDSET`

The first thing you should do is to tell ITS the correct century, date and time with `PDSET`:

    :pdset«
    (Please Log In)
    ___002 PDSET  IOTLSR

    PDSET.114

    Please don't use this program unless you know how.
    You are certain to break something if you happen to hit the wrong key.
    Type Control-Z to exit, or ? for a reminder of the commands.

The “Please Log In” message is a harmless reminder that you haven't told ITS your login name yet. It can be ignored for now.

First tell `PDSET` the correct century, since it will assume it is in the 1900s by default. Then tell it the date and time in YYMMDD and HHMMSS format. Any line which is messed up can be re-entered. When you are satisfied that it is correct, type `!.` (exclamation point, and then period).

For example, on July 20, 2003 at 3:02PM, you would type:

    20C
    030720D
    150200T
    !.
    113375/ 0       770201,,513056  ___002

    113374/ 0       3723    ___002
    IT IS NOW  3:02:00 PM EDT, SUNDAY, JUL 20,2003

Additionally, you may see some lines from `TARAKA` informing you that it is copying the ITS image.

    TARAKA DMPCPY .      _DMPCP OUTPUT WRITE  15:02:02
    TARAKA DMPCPY .      @      ITS    DELRNM 15:02:02

This is a normal function which `TARAKA` performs, and no cause for alarm. In any case, type `q` to leave the `PDSET` program.

    Q
    :KILL
    *

### Making the disk bootable, stage 1: `KSFEDR`

Now it is time to make the disk bootable, so that tape images no longer need to be mounted. This is done with the `KSFEDR` program:

    :ksfedr«
    (Please Log In)
    ERROR: File not found:  PK0000: .; .FEFS. PK0000
    !create«
    ___002 KSFEDR .      .FEFS. PK0000 WRITE  15:06:01
    FE filesystem DSK: .; .FEFS. PK0000 on pack #0.
    Directory address: 6600000004
    !write«
    Are you sure you want to scribble in the FE filesystem?  yes«
    Which file? bt«
    Input from (Default DSK: ___004; BT BIN): .;bt rp06«
    !quit«

    :KILL
    *

The above sequence creats a front-end filesystem on your disk, and write the RP06-specific bootstrap to it from the `MINSYS` installation. If this were a real KS10, you would also need to write a microcode file, but the simulated KS10 doesn't need it.

Make a note of the number after “Directory address” (`6600000004` in the sample above). You will need it in stage 2.

Note that you must affirm your desire to scribble in the FE filesystem with the full word “yes”; a simple “y” is not sufficient. Note also the `.;` (dot and semicolon) before `bt rp06` in the input filename.

Now use the `LOCK` program to take the system down, as so:

    :lock«
    (Please Log In)
    LOCK.154

    _5kill
    DO YOU REALLY WANT THE SYSTEM TO GO DOWN?
    y
    ___002 LOCK   SYS    DOWN   MAIL   WRITE  15:18:41

    PLEASE ENTER A BRIEF MESSAGE TO USERS, ENDED BY ^C

Since you're the only one on the system, you can just type `^C`. ITS will then complete the shutdown process (it takes about a minute):

    DB ITS going down in 5:00
    CULPRIT =  ___002 LOCK   15:19:06

    _
    DB ITS 1633 NOT IN OPERATION 15:19:06
    PFTHMG DRAGON CHANNA _DRGN_ TIMES  WRITE  15:19:06
    PFTHMG DRAGON CHANNA LOGOUT TIMES  DELRNM 15:19:06

    SHUTDOWN COMPLETE
    PI LEVEL 7 BUGDDT.  TYPE P TO CONTINUE.
    YOU ARE NOW IN DDT.
    BUGPC/   CAIA COFFI4+1   $Q-2/   JRST COFFI7

### Making the disk bootable, stage 2: `FESET`

Now that the system is down, type `^E` to get to the simulator's front-end console, and boot from tape unit 1 (the Salvager) again:

    ^E
    Simulation stopped, PC: 773034 (PUSHJ 1,773130)
    sim> b tu1«
    ITS MTBOOT.176

Use the `FESET` utility in Salvager to make the disk bootable:

    FESET$G'
    Set the FE filesystem directory pointer on the pack on unit #0
    Directory address: 6600000004«

    DDT

The directory address is the one you got from `KSFEDR` in stage 1. Now type `^E` to get back to the simulator front-end console and type `quit` to leave the simulator altogether:

    ^E

    Simulation stopped, PC: 773130 (SKIPN 5,32)
    sim> quit«
    Goodbye
    $

Now copy the configuration file, `init`, that you made at the beginning of this procedure, to the new name `boot`. Edit `boot` with a text editor and remove the following three lines:

    at tu0 minsys.tape
    at tu1 salv.rp06.tape
    at tu2 dskdmp.rp06.tape

since the tape images aren't needed anymore. Then add this line to the bottom of the file:

    b rp0

This tells the simulator to immediately boot from disk unit 0 when it is started.

### Booting ITS from disk

Now it is time to try out the new bootable disk you just made. Note that this piece of the installation is the normal bootup procedure for ITS and needs to be done every time you want to bring up the system:

    $ pdp10 boot«

    PDP-10 simulator V3.0-0

    DSKDMP

As before, load the standalone `.; @ ITS` from disk and start it with `ESC-g` as so:

    its«
    $G

    Salvager 255

    .TEMP. has no files, User File Directory DELETED

    DB ITS 1633 IN OPERATION
    DB ITS 1633 SYSTEM JOB USING THIS CONSOLE.
    THE KS-10 CLOCK HAS BEEN RESET, IF THE TIME CANNOT
    BE DETERMINED FROM THE NETWORK, YOU MAY HAVE TO :PDSET
    LOGIN  TARAKA 0
    TOP LEVEL INTERRUPT 40 DETACHED JOB # 2, USR:TARAKA DRAGON

Login with `^Z` and use `PDSET` as previously described to set the current time.

At this point, you have a minimal multiuser ITS system.

Mirian Crzig Lennox