I was impressed to learn that when Margaret Hamilton programmed this machine, she wrote an interpreter, and coded the mission logic in the interpreted language. So, in a sense, it really was microcoded; but the microcode was what looks like the real instruction set, and the instructions actually used lived in ROM.

The Xerox Alto, which was used for the original Smalltalk in 1972, also worked much this way: It had 16 program counters, one of which pointed to a program for interpreting Alto instructions. Other program counters were for refreshing the screen, operating the disk, driving the laser printer, and moving network packets. An interrupt just changed which program counter instructions came from.

The Smalltalk runtime was another interpreter, interpreted by Alto (interpreted) instructions. People complained about how slow Altos were, no surprise.

I might have misremembered some of the details above. Corrections welcome.