I should add that the D machines had writable control stores so these language environments (Interlisp-D, SmallTalk, and Cedar/Mesa) each had custom microcode.

I should add that the D machines had writable control stores so these language environments (Interlisp-D, SmallTalk, and Cedar/Mesa) each had custom microcode. I wrote some microcode for InterLisp-D back when I was 20.