Symbolics, Inc.[2] was a computer manufacturer headquartered in Cambridge, Massachusetts, and later in Concord, Massachusetts, with manufacturing facilities in Chatsworth, California (a suburban section of Los Angeles). Its first CEO, chairman, and founder wasRussell Noftsker.[3] Symbolics designed and manufactured a line of Lisp machines, single-user computers optimized to run the Lisp programming language. Symbolics also made significant advances in software technology, and offered one of the premier software development environments of the 1980s and 1990s, now sold commercially as Open Genera for Tru64 UNIX on the HP Alpha. The Lisp Machine was the first commercially available "workstation" (although that word had not yet been coined).
Symbolics was a spinoff from the MIT AI Lab, one of two companies to be founded by AI Lab staffers and associated hackers for the purpose of manufacturing Lisp machines. The other was Lisp Machines, Inc., although Symbolics attracted most of the hackers, and more funding.
Symbolics' initial product, the LM-2 (introduced in 1981), was a repackaged version of the MIT CADR Lisp machine design. The operating system and software development environment, over 500,000 lines, was written in Lisp from the microcode up, based on MIT's Lisp Machine Lisp.
The software bundle was later renamed ZetaLisp, to distinguish the Symbolics' product from other vendors who had also licensed the MIT software. Symbolics' Zmacs text editor, a variant of Emacs, was implemented in a text-processing package named "ZWEI", an acronym for "Zwei was Eine initially" — "Eine" being an acronym for "Eine Is Not Emacs" (both recursive acronyms and puns on the German words for "One" ("Eins", "Eine") and "Two" ("Zwei")).
The Lisp Machine system software was then copyrighted by MIT, and was licensed to Symbolics. Until 1981, they shared all the source code with MIT and kept it on an MIT server. According to a Symbolics employee,[who?] the reason for the change in policy was Richard Stallman's making changes with which they disagreed, such as removing Symbolics' copyright notices on Symbolics' produced enhancements and transferring the resulting enhancements to the other commercial licensees, and at one point leaving the software in a state where it would not compile.[citation needed] Richard Stallman's account claims Symbolics engaged in a business tactic in which it forced MIT to make all fixes and improvements to the Lisp Machine OS available only to it, and thereby choke off its competitor LMI, which at that time had insufficient resources to independently maintain or develop the OS and environment.[4]
Symbolics felt that they no longer had sufficient control over their product. At that point, Symbolics began using their own copy of the software, located on their company servers — while Stallman says that Symbolics did that to prevent its Lisp improvements from flowing to Lisp Machines, Inc. From that base, Symbolics made extensive improvements to every part of the software, and continued to deliver almost all the source code to their customers (including MIT). However, the policy prohibited MIT staff from distributing the Symbolics version of the software to others. With the end of open collaboration came the end of the MIT hacker community. As a reaction to this, Stallman initiated the GNU project to make a new community. Eventually, Copyleftand the GNU General Public License would ensure that a hacker's software could remain free software. In this way Symbolics played a key, albeit adversarial, role in instigating the free software movement.
The 3600 Series:
In 1983, a year later than planned, 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 implementation 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 forerror-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 bymultitasking 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 allowwire-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 that could support the ZetaLisp software was 14 inches (356 mm) across (most 3600s shipped with the 10½-inchFujitsu Eagle). The 3670 and 3675 were slightly shorter in height, but were essentially the same machine packed a little tighter. The advent of 8 inches (200 mm), and later 51⁄4 inches (130 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 3640s. 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 lower priced variant of the 3620, essentially identical in every way except that it was licensed for application deployment rather than general development.
