The MIT Lisp machine
In August 1977 the group at MIT's Artificial Intelligence Laboratory reported an almost complete system running on the Lisp machine prototype. It is a personal computer whose instruction set, the memo says, was designed specifically for Lisp, the language of AI research; a complete machine would cost about $80,000.
Why it matters
Instead of sharing the time of a large PDP-10 among many people, the group proposed to give each AI researcher a machine of their own built for their language. A program's speed no longer depended on how many people were working at once. This is the class of special-purpose AI hardware whose market collapsed in the late 1980s.
By Greenblatt's working paper of November 1974 the goal was single-user operation without time-sharing at about $70,000 a system. Tom Knight's CONS processor had 32-bit data paths, 24-bit addresses and a large microcode store, 16K 48-bit words, that executes Lisp instructions. The 1977 memo says the prototype was built somewhat more than two years earlier without memory or input-output, and got memory, a disk and a terminal at the beginning of 1977. The LUNAR query system ran on it about three times as fast as in Maclisp on the KA-10; the group planned seven machines for late 1977 and early 1978. In May 1979 AI Memo 528 describes CADR, a revised CONS, a general-purpose 32-bit microprogrammable processor on which the Lisp machine rests. What the record does not claim: that this was the first machine designed for an AI language, or how many CADRs were eventually built; the documents read do not say.