-rw-r--r-- 1108 LICENSE.txt
-rw-r--r-- 505 Makefile
-rw-r--r-- 2851 README.md
-rw-r--r-- 3084 client.md
-rw-r--r-- 3244 server.c


The programs contained in this directoy allow bootstrapping of a completely blank PDP-11 from an external host. It is not required that the PDP-11 have any pre-existing code in the form of drives or ROMs.


The client has been tested with a PDP-11/23+ (KDF11-B on SLU2) and a PDP-11/73 (KDJ11-B with DLV11-J). It should work with most PDP-11 CPUs and SLUs which are compatible with the DLV11-J register layout.

The server has been tested with a PC running FreeBSD.


These instructions assume your PDP-11 has a serial connection to a UNIX host, the bootstrap_server.c program has been compiled on the UNIX host, and the UNIX host has a binary image ready for transfer to the PDP-11.

Begin by loading the program contained in client.md into the PDP-11 via the frontpanel switches or ODT. Set the PDP-11’s CPU registers as follows.

Begin execution on the PDP-11. If the bootstrap program was loaded at the memory addresses listed in client.md, begin execution at address 70000.

Initiate the transfer from the UNIX host with the command

pdp11-serial-loader -i <binary> -o <port>

where <port> is the path to the device file for the serial port connected to the PDP-11 and <binary> is the path to the binary image file. For example, if using the first serial port under FreeBSD and a binary image named pdp11.bin, execute this command.

pdp11-serial-loader -i pdp11.bin -o /dev/cuau0

In FreeBSD, add your user to the dialer group for permission to access the serial port.

pw groupmod dialer -m ataylor
exec su -l ataylor

Once the binary image has transferred to the PDP-11, it will begin execution at the address contained in R3 which should be your code.

Binary Image Format

Since the bootstrap program must be manually toggled into the PDP-11, brevity is paramount. Thus, the binary image matches the little-endian byte ordering of the PDP-11 word.

Consider the following example program.


This would correspond to a binary image with consecutive bytes of:

Byte Value
0 00000000
1 00001010
2 00000001
3 00010000

If loaded into memory starting at location 2000, the PDP-11’s memory would look like this:

Address Value
2000 0000101000000000
2002 0001000000000001