Design of LISP-Based Processors

I found this paper by Guy Steele and Gerald Sussman describing the design of a LISP-interpreting processor (from Jaap Weel).

The paper shortly describes a small subset of LISP and a meta-circular evaluator, quickly moving on to describing an interpreter on a register-machine, and then implementing this interpreter as a VLSI processor. The resulting CPU lacks an ALU (it uses an incrementor for garbage collector purposes), but arithmetic is not necessary for most symbol-manipulating programs (pattern matching, symbolic maths).

The LISP processor consists of two state-machines (the evaluator and the garbage collector). It would be fun to build such a system using today’s low-cost micro-controllers, not following the approach of building a LISP-compiler targeting micro-controllers, but building a “micro-LISP-machine”.