Background · Lisp machines

The VLM

The Virtual Lisp Machine is Symbolics' emulator of its Ivory processor. It runs Genera, the operating system of the Symbolics Lisp machines, on conventional computers, and it is the program this project runs on bare metal.

What the VLM is

Symbolics built Lisp machines: computers whose processors execute Lisp directly, with type tags on every word of memory, and whose whole software, from the device drivers to the development environment, is written in Lisp. The last of these processors is Ivory, a single-chip Lisp microprocessor with 40-bit words: 8 bits of tag and 32 bits of data or address.2,9

The VLM, the Virtual Lisp Machine, emulates the Ivory instruction set in software. Symbolics shipped it in 1993 as Open Genera, on DEC Alpha workstations; today, as Portable Genera, it runs the same Genera world on x86-64 and Arm64 computers under Linux and macOS.3,13,14 On the host it runs as an ordinary program: Genera draws its screen through X11 and reads the host's files over NFS. Genera on Bare Metal gives the VLM's emulator the computer itself.

The Lisp Machine at MIT

In 1973 Richard Greenblatt and Thomas Knight began the Lisp Machine project at the MIT Artificial Intelligence Laboratory, to build computers that run Lisp in hardware. Their first machine was CONS; its successor, the CADR, was shown at an AI conference at MIT in 1978, and DARPA funded its construction. About 25 CADRs were built and used in and outside MIT.1,6 The Lisp Machine's software introduced Flavors, Howard Cannon's object system, which shaped the Common Lisp Object System that followed.17

Symbolics and LMI

Two companies took the Lisp Machine out of MIT. Greenblatt founded Lisp Machines, Inc. (LMI) in 1979; Russell Noftsker and others founded Symbolics in April 1980. Both licensed the MIT Lisp Machine software.4,2,7 Symbolics' first product, the LM-2 of 1981, was a repackaged CADR. Its own design, the 3600 with a 36-bit tagged word, followed in 1983, and the 3600 family grew through the 1980s with the 3640, 3670, 3645, 3675, 3650 and others.2,8 Texas Instruments licensed LMI's design in 1983 and built the TI Explorer on it; LMI went bankrupt in 1987.4,5 On 15 March 1985 Symbolics registered symbolics.com, the first .com domain name.2,16

Genera

Genera is the operating system and development environment of the Symbolics machines, descended from the MIT Lisp Machine system and named Genera in the mid-1980s. It is written entirely in Lisp, down to the device drivers, the garbage collector, the scheduler and the network protocols, and it is object-oriented throughout, with Flavors and later CLOS. Genera comes with its source code, and code, data and tools share one address space.3,14 Its presentation-based window system, Dynamic Windows, arrived with Genera 7 in 1986; the Document Examiner shows the manuals as hypertext; Zmacs is its Emacs and Zmail its mail reader. Genera speaks TCP/IP and Chaosnet and reaches files over NFS and FTP.3 Genera 8, in 1990, ran on both the 3600 and the Ivory machines and brought CLOS; 8.1 added CLIM, and 8.3 came on CD-ROM in 1993.3,11

Ivory

Ivory put the Lisp machine on a single chip. Symbolics presented it in 1987 as a 40-bit tagged Lisp microprocessor and built a range of machines around it: the XL400 workstation and the MacIvory board for the Apple Macintosh in 1988, the UX400 board for Sun workstations in 1989, the XL1200 and UX1200 in 1990, MacIvory III in 1991 and the NXP1000 in 1992.10,9,2

Open Genera and Portable Genera

Open Genera 1.0, in 1993, introduced the VLM on DEC Alpha workstations under OSF/1, later Digital UNIX and Tru64; Open Genera 2.0, at the end of the 1990s, ran several Genera instances on one Alpha.3,13 The company filed for Chapter 11 protection in January 1993, and its assets and name were sold in 1995; Symbolics continued, maintaining its customers' systems.12,2 Around 2007 Brad Parker made the VLM run on x86-64 Linux, an unofficial port.15,3 Symbolics Technologies released Portable Genera 2.0 in 2021: the VLM for x86-64 and Arm64, under Linux and macOS, including Apple silicon, with Gary Palter as the author of the x86 and Arm emulators. Updates follow regularly; Portable Genera 2.0.6 appeared in August 2024.3,14,18 The x86-64 emulator of Portable Genera is the one this project runs on the bare laptop.

Timeline

The timeline gives the dates of this history, from the MIT Lisp Machine project in 1973 to Portable Genera and Genera on Bare Metal.

Sources

  1. Lisp machine, Wikipedia.
  2. Symbolics, Wikipedia.
  3. Genera (operating system), Wikipedia.
  4. Lisp Machines (LMI), Wikipedia.
  5. TI Explorer, Wikipedia.
  6. The MIT CADR FAQ, unlambda.com.
  7. Symbolics, LM-2 product announcement and MIT Lisp Machine license press release, 1980, bitsavers.
  8. Symbolics, 3600 Technical Summary, February 1983, bitsavers.
  9. Symbolics, I-Machine Architecture Specification, bitsavers.
  10. C. Baker et al., The Symbolics Ivory processor: a 40 bit tagged architecture Lisp microprocessor, IEEE ICCD 1987.
  11. Symbolics, Genera 8 release notes and Open Genera documentation, bitsavers.
  12. Symbolics bankruptcy filed and Symbolics assets bought, smbx.org.
  13. History, Symbolics Technologies.
  14. Genera, Symbolics Technologies.
  15. VLM on Linux, CLiki.
  16. 25 years later, first registered domain name changes hands, TechCrunch, 2009.
  17. Flavors, Wikipedia.
  18. Symbolics Technologies, LLC, GitHub.