

In 1983, Symbolics introduced the 3600 family of Lisp machines. Code-named the "L-machine" internally, the 3600 family was an innovative new design, inspired by the CADR architecture but sharing few of its details. The main processor had a 36 bit word (divided up as 4 or 8 bits of tags, and 32 bits of data or 28 bits of memory address). Memory words were 44 bits, the additional 8 bits being used for error-correcting code (ECC). The instruction set was that of a stack machine. The 3600 architecture provided 4,096 hardware registers, of which half were used as a cache for the top of the control stack; the rest were used by the microcode and time-critical routines of the operating system and Lisp run-time environment. Hardware support was provided for virtual memory, which was common for machines in its class, and for garbage collection, which was unique.
The original 3600 processor was a microprogrammed design like the CADR, and was built on several large circuit boards from standard TTL integrated circuits, both features being common for commercial computers in its class at the time. CPU clock speed varied depending on the particular instruction being executed, but was typically around 5 MHz. Many Lisp primitives could be executed in a single clock cycle. Disk I/O was handled by multitasking at the microcode level. A 68000 processor (known as the "Front-End Processor", or FEP) started the main computer up, and handled the slower peripherals during normal operation. An Ethernet interface was standard equipment, replacing the CHAOSnet interface of the LM-2.
The 3600 was roughly the size of a household refrigerator. This was partly due to the size of the processor - the cards were widely spaced to allow wire-wrap prototype cards to fit without interference - and partly due to the limitations of the disk drive technology in the early 1980s. At the 3600's introduction, the smallest disk drive that could support the ZetaLisp software was 14 inches (356 mm) across (most 3600s shipped with the Fujitsu Eagle)! The 3670 and 3675 were slightly shorter in height, but were essentially the same machine packed a little tighter. The advent of 8 inch (203 mm), and later 5 1/4 inch (133 mm), disk drives that could hold hundreds of megabytes led to the introduction of the 3640 and 3645, which were roughly the size of a two-drawer file cabinet.
Later versions of the 3600 architecture were implemented on custom integrated circuits, reducing the 5 cards of the original processor design to 2, at a large manufacturing cost savings but with performance slightly better than the old design. The 3650, first of the "G machines" (as they were known within the company), was housed in a cabinet derived from the 3640's. Denser memory and smaller disk drives enabled the introduction of the 3620, about the size of a modern full-size tower PC. The 3630 was a "fat 3620" with room for more memory and video interface cards. The 3610 was a stripped-down, low-priced variant of the 3620 for cost-sensitive customers.
The various models of the 3600 family were popular for artificial intelligence (AI) research and commercial applications throughout the 1980s. The AI commercialization boom of the 1980s led directly to Symbolics' success during the decade. Symbolics computers were widely believed to be the best platform available for developing AI software.
Also contributing to the 3600 series' success was a line of bit-mapped graphics color video interfaces, combined with extremely powerful animation software. Symbolics's Graphics Division, headquartered in Westwood, California, a stone's throw from the major Hollywood movie and TV studios, made its S-Render and S-Paint software into industry leaders in the animation business.
As well, Symbolics developed the first workstations capable of processing HDTV quality video, which enjoyed a popular following in Japan. A 3600 — with the standard black-and-white monitor — made a cameo appearance in the movie Real Genius (1985). Symbolics' Graphics Division was sold to Nichimen Trading Company in the early 90s, and the S-Graphics software ported to Franz Allegro Common Lisp on SGI and PC computers running Windows NT. Today it is sold as Mirai by Izware LLC., and continues to be used in major motion pictures (most famously in New Line Cinema's Lord of the Rings), video games and military simulations.
Symbolics 3600 series computers were also used as the first front end "controller" computers for the Connection Machine massively parallel computers manufactured by Thinking Machines Inc., another MIT spinoff based in Cambridge, Massachusetts. The Connection Machine ran a parallel variant of Lisp and, initially, was used primarily by the AI community, so the Symbolics Lisp machine was a particularly good fit as a front-end machine.
For a long time, the operating system didn't have a name, but was finally named "Genera" around 1984. The system included a number of advanced dialects of Lisp. Its heritage was MACLISP on the PDP-10, but it included more data types, and multiple-inheritance object-oriented programming features.
Initially called Lisp Machine Lisp, then ZetaLisp, it finally acquired the name "Symbolics Common Lisp" during the creation of Common Lisp in 1987. Common Lisp is a subset of the dialect available on the Lisp Machine.



