MC's journal

Boomtime, the 64 day of Discord in the YOLD 3181

Symbolics and the Lisp machines

Some time ago the first domain name in DNS,, turned 30 years old. WHOIS says:

Sponsoring Registrar IANA ID: 2
Whois Server:
Referral URL:
Status: clientTransferProhibited
Updated Date: 05-jun-2011
Creation Date: 15-mar-1985
Expiration Date: 16-mar-2016

Behind the domain name was once Symbolics, Inc., a legendary manufacturer of Lisp machines, computers with a special architecture suitable to run Lisp programs at high speed.

There's something in the eye of an old hacker when she thinks about Lisp machines. From what I can gather, they seem to have been the ultimate hacker computer: a completely dynamic environment with easy access to source for everything, including the lowest levels of the operating system, easily changed from within the interactive environment with the effects taking place immediately.

There were several LispM makers back before the AI Winter: Symbolics, LMI, Xerox and even Texas Instruments, with their TI Explorer. A brief history of lisp machines can be found here:

I'm too young to have experienced the LispM directly myself. When I started at Linköping University the Computer Science department had just thrown out some Xerox LispMs and replaced them with Sun SPARCstation-1s. They still ran some Lisp assignments in an emulator called Medley but since I didn't even had official access to the the Suns, I never experienced it.

I don't know where the Xerox machines ended up. For some reason Lysator, the academic computing society at LiU, didn't get them. Update, Lysator's counterpart in Uppsala, has a few Symbolics machines.

To get a feeling of what it was like to work on a LispM, here's a movie of someone playing with a TI Explorer in Unisys disguise for an hour:

and here's a collection of screenshots from Symbolics' Genera environment:

Remember that many of these screenshots are from the early 1980s, before the first Mac, for instance.

The CPU in most of the LispMs were developed from the architecture of the CONS and CADR machines from MIT's AI Lab. Both Symbolics' and LMI's first machines was based directly on the CADR.

For a couple of years it's been possible to run the CADR machine on an emulator written by Brad Parker. All the source from the original CADR system is also available:

Björn Victor has collected some information about running emulated LispMs:

Some people still seem to dream about running Lisp on the bare metal. Here are two such projects:

Other than that, the best way of experiencing something like the LispM environment on modern computers is probably to use Emacs as your main environment. This is what I do, although I have sometimes looked longingly at Racket.

Written by MC using Emacs and friends.