Levy_S-Hackers-Heroes-Computer-Revolution

could easily handle the considerable demands that LISP put on a machine. So inthe early seventies Greenblatt started to design a computer which would run LISPfaster and more efficiently than any machine had done before. It would be a singleusermachine finally a solution to the esthetic problem of time-sharing, where thehacker is psychologically frustrated by a lack of ultimate control over the machine.By running LISP, the language of artificial intelligence, the machine would be apioneering workhorse of the next generation of computers, machines with theability to learn, to carry on intelligent dialogues with the user on everything fromcircuit design to advanced mathematics.So with a small grant, he and some other hackers notably Tom Knight, who hadbeen instrumental in designing (and naming) the Incompatible Time-sharingSystem began work. It was slow going, but by 1975 they had what they called a"Cons" machine (named for the complicated "constructor operator" function thatthe machine performed in LISP). The Cons machine did not stand alone, and hadto be connected to the PDP-10 to work. It was two bays wide, with the circuitboards and the tangle of wires exposed, and they built it right there on the ninthfloor of Tech Square, on the uplifted floor with air-conditioning underneath.It worked as Greenblatt hoped it would. "LISP is a very easy language toimplement," Greenblatt later explained. "Any number of times, some hacker goesoff to some machine and works hard for a couple of weeks and writes a LISP. 'See,I've got LISP.' But there's a hell of a difference between that and a really usablesystem." The Cons machine, and later the stand-alone LISP machine, was a usablesystem. It had something called "virtual address space," which assured that thespace programs consumed wouldn't routinely overwhelm the machine, as was thecase in other LISP systems. The world you built with LISP could be much moreintricate. A hacker working at the machine would be like a mental rocket pilottraveling in a constantly expanding LISP universe. For the next few years theyworked to get the machine to be a stand-alone. MIT was paying their salaries, andof course they were all doing systems work on ITS and random AI hacking, too.The break came when ARPA kicked in money for the group to build six machinesfor about fifty thousand dollars each. Then some other money came to build moremachines.Eventually the hackers at MIT would build thirty-two LISP machines. From theoutside, the LISP computer looked like a central air-conditioning unit. The visualaction all occurred in a remote terminal, with a sleek, long keyboard loaded withfunction keys and an ultra-high-resolution bit-mapped display. At MIT the ideawas to connect several LISP machines in a network, so while each user had fullcontrol he could also be hacking as part of a community, and the values arisingfrom a free flow of information would be maintained.