You would not really need a specialized CPU anymore for a Lisp Machine. Those CPUs were invented to keep instructions small and efficient, provide large address

You would not really need a specialized CPU anymore for a Lisp Machine. Those CPUs were invented to keep instructions small and efficient, provide large address spaces and enable simple compilers. In the last part of the 80s the trend to RISC CPUs was clear and several RISC CPUs were developed for Lisp, but they did not reach the market anymore. The SPARC cpu was mildly inspired by Lisp / Smalltalk. Since new CPUs were not happening for Lisp (there was no money for it), two of the existing CPUs were ported as VMs to other processors (Symbolics Ivory to ALPHA because of its 64bit support) and the Xerox Lisp system was ported to x86 and SPARC. Besides the CPU there is another, even more important, difference. Lisp systems were all the way down to the metal developed in Lisp. Mathematica is largely written in C++ (runtime, environment, ...) and runs on top of a conventional OS (Windows, OSX, Linux, ...).