I was talking (on-line) with a friend of mine, who has nothing to do
with computers or hacking, and he asked me exactly this: What's a
Lisp-CPU? How would you explain it in one or two paragraphs? Imagine
that he's a guy who owns a computer, knows what a CPU is (more or
less), has some amateurish interest in the technology of computers. He
has taken apart some Intel boxen and reassembled them, and probably
had one or two programming classes in college.
The Lisp-CPU we're talking about is of the AIM-514 variety.
Thanks for any suggestions
/npat
Nick Patavalis wrote:
> I was talking (on-line) with a friend of mine, who has nothing to do
> with computers or hacking, and he asked me exactly this: What's a
> Lisp-CPU? How would you explain it in one or two paragraphs? Imagine
> that he's a guy who owns a computer, knows what a CPU is (more or
> less), has some amateurish interest in the technology of computers. He
> has taken apart some Intel boxen and reassembled them, and probably
> had one or two programming classes in college.
>
> The Lisp-CPU we're talking about is of the AIM-514 variety.
I'm guessing "AIM-514" means MIT AI Memo 514, which is Steele and
Sussman's paper on their Scheme chip. That is a microprocessor whose
instruction set is a set of primitives for executing programs in the
Scheme dialect of Lisp. The chip represents data using 32-bit words in
which 1 bit is dedicated for the use of the on-chip garbage collector.
Some of the registers are:
VAL - the last value produced by evaluating a Lisp form
ARGS - a list containing any forms that are about to be evaluated
DISPLAY - a list of argument lists for pending functions
EXP - the current expression that iis about to be evaluated
STACK - activation records for functions that are waiting to return
NEWCELL - the next available free memory
(taken from Kogge's _The Architecture of Symbolic Computers_)
There have been various other Lisp machines, all of them with various
hardware features designed particularly to make Lisp run very
efficiently. Most did not go as far as the Scheme chip in literally
building the language evaluator into the hardware.