Why Lisp? Everyone "knows" that lisp was the language of choice for Artificial Intelligence research, but a big part of AI research is about paradigms for representing knowledge, expressing algorithms, man-machine communication, and machine-to-machine communication: In short, how to use computers in general. Lisp, as the default AI language, was also an important research vehicle for new computer languages, networking, display technology and so on.
Why Lisp Machines? The standard platform for Lisp before Lisp machines was a timeshared PDP-10, but it was well known that one Lisp program could turn a timeshared KL-10 into unusable sludge for everyone else. It became technically feasible to build cheaper hardware that would run lisp better than on timeshared computers. The technological push was definitely from the top down; to run big, resource hungry lisp programs more cheaply. Lisp machines were not "personal" out of some desire make life pleasant for programmers, but simply because lisp would use 100% of whatever resources it had available. All code on these systems was written in Lisp simply because that was the easiest and most cost effective way to provide an operating system on this new hardware.
Why two different kinds? Quite a few groups with different goals were building high priced, high powered workstations at about the same time. All were capitalizing on Moore's law and the emerging consensus that bitmapped displays, windows, mice, and networks were effective paradigms. The C/Unix community spawned Sun, Apollo, and Silicon Graphics. The Pascal Community spawned the PERQ. There were two major branches in the Lisp family tree, Interlisp and Maclisp, so it should be no surprise that there were two main family branches in Lisp machines.
Today, all this hardware and software are commercially extinct, but many features that were commercialized by lispms are present in every PC.
For more recollections and speculations about this fascinating era
of cyber-history, consult the Lispm FAQ
and Oral History
|1975|| The CONS prototype
random logic, 24 bit address
AI Memo 444
|1977||The CADR aka MIT Lisp Machine aka Greenblatt
24 bit address
AI Memo 528
(aka "D0") Used hardware to the Xerox Alto, but bigger, faster and with memory mapping hardware.
|1980||LM-2 Symbolics Lisp Machine, essentially a repackage CADR||LMI Lisp Machine same as CADR|
Used the same hardware as the original Xerox Star.
|1982||L-Machine 28 bit address
Symbolics 3600, later 3640, 3670
|1983||LMI Lambda||TI Explorer same as LMI Lambda||Dorado custom hardware from Xerox PARC.
Originally for internal use, but a few were sold.
|1984||G-Machine Custom gate arrays, 28 bit address
Symbolics 3650, later 3620, 3630
about 20 person-years in an effort to port Zetalisp to their
hardware. They eventually had a working, if slow, prototype.
|Integrated Inference Machines
Custom hardware and firmware. They had working prototypes and a few production models..
|1987||I-Machine Custom LSI, 32 bit address
Explorer-II custom LSI
|1989||I-Machine Custom LSI
NXP1000 "pizza box"
|1992||NXP1000 (pizza box)
Virtual Lisp Machine (aka Open Genera)
i-machine compatible, running on Dec Alpha Processor
|...||Sunstone (planned super lispm)
Open Genera forAlpha can still be purchased from the remains of Symbolics.
|Explorer-III software Explorer-II emulator||The last generation of Interlisp-D was called "Medley",
because it combined Interlisp and Common Lisp. It ran on several
PC OSs (but apparently not windows). Google "Medley" and
"Interlisp-D" for current status.