Re: The PDP-11 lives on
Another extremely elegant machine was the PDP-10 aka DecSystem-10/DecSystem-20. With a 36 bit word length and variable byte size (six bit was most often used, but was by no means the only one), each instruction took up one word/36 bits. Every instruction consists of a 9-bit opcode, a 4-bit register code, and a 23-bit effective address field, which consists in turn of a 1-bit indirect bit, a 4-bit register code, and an 18-bit offset or alternatively an immediate value. Early machines used ferrite core memory, meaning they could be run at arbitrary clock speeds, down as low as one instruction cycle per second or so, all controlled by two knobs on the console. Great fun to watch the lights slowly cycle through as a program ran.