There is a bit to much simplification here, and confusing terminology going on here. Lisp Machines did not have "processes" (as in, Unix processes); a Lisp Machine process just a function - with some special properties.
The Lisp Machine only had one processor for the Lisp Machine, and it did absolutely support multi-processing and multi-threading.
A good explanation can be found in the Lisp Machine manual:
The Lisp Machine only had one processor for the Lisp Machine, and it did absolutely support multi-processing and multi-threading.
A good explanation can be found in the Lisp Machine manual:
Which is also where all current work on the MIT Lisp Machine is being done. :-)