After a read through of Will Kranz’s article I decided to opt for an oversized tape image (10MB) using Will’s modified TU58 (dd.sys) driver. The standard TU58 is only 256KB is size and this larger capacity should give plenty of space for applications.

To build the tape, here are the steps to go through:

Creating a basic image via SIMH

SIMH is an excellent PDP-11 emulator and an invaluable tool for building working disk and tape images for use on your real PDP. To create the RT-11 tape, download the RT-11 software kit from the SIMH site and setup the PDP-11 emulator with the following configuration:

SET CLK 50HZ
SET CPU 11/73
SET CPU 2048K

SET RL ENABLED
SET RL0 RL02
ATT RL0 share/pdp11/disks/rl02/rt11-v53.rl02.dsk
SET RL1 RL02
ATT RL1 share/pdp11/tapes/tu58/rt11.tap

BOOT RL0

You will need to adjust the locations of your disk images to match your setup.

Once booted into RT11, run the following sequence of commands to create a bootable image on the RL1 disk:

INITIALIZE DL1:
COPY/SYSTEM DL0:*.* DL1:
COPY/BOOT:DD DL1:RT11SJ.SYS DL1:

The result of this is an image with a TU58 boot sector, however its still using the original 256KB based driver. The next step is to get the modified driver into place.

Installing the modified TU58 driver

To install the modified TU58 driver:

• Downloaded the DW.SYS driver from Will’s site.
• If you are using Linux, install DOSEMU, an MS-DOS emulator. This will allow you to use the PUTR program below.
• Download John Wilson PUTR application. PUTR allows you to mount various PDP file formats from an MSDOS machine and copy files to and from the filesystems. This makes it a highly useful piece of kit for moving stuff from your PC to your -11.
• Fired up PUTR and copy the downloaded DW.SYS device driver onto the image you created on SIMH.
• Exit PUTR and boot back into PUTR (using same config as before)
• Make the new device driver the boot device by running the command COPY/BOOT:DW DL1:RT11SJ.SYS DL1:

You should now have a ready to go TU58 tape image.

The TU58 is an ideal first device to emulate as its only requirement of the PDP-11 is a spare serial port which the vast majority of machines should be able to offer.

There are a few different options out there:

• Dan Ts’o Emulator – The original TU58 software emulator from which most others are derived. Designed to compile under BSD unix. Requires modification to get to run under a modern linux distribution
• Spare Time Gizmos TU58 Emulator – A very elegant hardware based solution.
• Will’s Emulator – Derived from the Dan Ts’o emulator but updated to compile under Linux. I had some problems compiling this on more modern versions of Linux although after a bit of tweaking built fine.
• Don North’s Emulator – An update on the Dan Ts’o emulator and designed to run under cygwin on Windows. This version has many neat additional features such as enhanced debug/logging. Compiled under linux (Centos4/Redhat Enterprise 4) and worked first try.

Having compiled up and tested as many of the above as I could, I decided to go with Don North’s emulator. Its enhanced debugging/logging output and ease of compilation makes it the best choice in my opinion.

If you would like to try installing it yourself, here are the steps:

1. Download tu58em_v1.4c.zip
2. Unzip it
3. Go into the extracted directory and type “make”
4. The emulator binary ‘tu58em’ should now exist in this directory.

On Centos linux, the above is achieved with the following commands:

wget http://www.pdp11.co.uk/wp-content/gallery/tu58-emulator/tu58em_v1.4c.zip
unzip tu58em_v1.4c.zip
cd tu58em_v1.4c
make

Once you have a working binary, you need to download some tape images to use with it. You can find some XXDP images from Will Kranz’s site here.

Now you should have everything you need at the emulator end to boot your PDP-11. Next you need to set up a SLU on your -11 and set it to an appropriate baud rate. I used a DLV11-J and configured its first port to 9600 baud 8-n-1. The final step is to connect a serial cable between the emulator PC and your -11

Having got everything in place, fire up your tu58 emulator, making sure you have specified the correct baud rate on the command line (if you omit a baud rate setting it will default to 9600). Here is an example that I found to work:

tu58em -m -x -v -p /dev/ttyS0 -w XXDPD2D.TAP

Now fire up your PDP-11. You will now need to enter a bootstrap. I was lucky and already had a suitable bootstrap ROM in my 11/23+. If you do not have this, you will need to find a suitable bootstrap. I will add these to this page as soon as I have located.