Finally we come to the lowest level in our description of the typical computer system. Each level of abstraction hides the details that are unnecessary for the user at the next-higher level. The details at Level LG1 are hidden from the user at Level ISA3, the instruction set architecture level. Remember that the user at Level ISA3 sees a von Neumann machine whose language is machine language. The job of the designer at Level LG1 is to construct the Level ISA3 machine. These last three chapters describe the language and design principles at Level LG1 that are required to construct a von Neumann machine.
The figures in this book consistently show the microcode level between the instruction set architecture level ...