It wasn't Lisp all the way down in the Lisp Machine design--it was a microcoded engine, of course. Though, yes, the system software was written in Lisp. There

It wasn't Lisp all the way down in the Lisp Machine design--it was a microcoded engine, of course. Though, yes, the system software was written in Lisp. There was a front-end processor (designed by Howard Cannon, who also was the main designer of the Flavors system) which loaded the microcode and booted up the main processor.