Pretty sure the https://en.wikipedia.org/wiki/IBM_704 was the first Lisp machine (as CAR, CDR come from register names on the 704...)
But DEC did rule academic computing well into the 80s.
But DEC did rule academic computing well into the 80s.
But the PDP-6 was a different class of device as every machine word was (could store) a cons; the common list manipulation functions (not just car and cdr but rplaca et al) were actual machine instructions etc (even if the names were different, e.g. CAR was HLRZ, as I can still remember).
In other words, lisp was implemented _on_ the IBM machine while the design of the 6/10 architecture was influenced by the needs of lisp. Both Marvin and Gordon independently confirmed this to me.