MIT CADR Lisp Machine FAQ

updated 9/29/2005


What is this?
This is some information about one of MIT's Lisp machines and some notes on lisp machines in general. Lisp machines are a class of computers which were designed to run the LISP language. They generally run LISP from top to bottom, including the entire operating system and drivers.

There are better places for to learn the history, but in the mid '70s the "AI Labs" at MIT designed a machine called the CADR. This was their second machine and the first one was called the CONS.

MIT built a handful (20-30?) CADR machines and used them extensively. Later when Symbolics Corporation was formed they cleaned up the CADR design and sold it as the LM-2 (affectionately known by Symbolics employees as "the dog" because of it's blazing speed).

So what is here at this site?
I have resurrected some of the software from the original CADR and written a microcode simulator which will boot the original software. I and some others are working on getting the "simulated CADR" to talk via the network to a file server and a simulated PDP-10 running ITS. You can find the CADR software here.

As we make progress I'll try and keep the site up to date. Our current goal is to get the CADR booted and talking to a file server.

Who owns the lisp code?
MIT hold the copyrights to the CADR source code. They have graciously allowed me to redistribute the software with a copyright notice.

I thought all the old lisp machine code was lost!
Yes, many people told me it was lost and never to be found. Don't believe what you hear on the net (or anywhere :-). It turns out it was all waiting to be found - you just had to know where to look.

I have been able to find tapes from various people and a large collection of backup tapes from MIT. In time I suspect all of the old AI Labs files will be recovered and made available. This includes all of the CADR files and software.

What about Symbolics?
Symbolics split off from the AI labs and formed a corporation. The created the LM-2, the 3600 line and the Ivory based machines. They hold the copyrights to software they created. The have not, to date, allowed any of their software to be distributed.

Symbolics today is owned by one person and is really just a maintaince group for old lisp machines. The sole owner recently passed away and all of the software is now in probate. A group of ex-symbolics people are working to free the software and get it released. We're hoping for something in the summer of 2006.