[lou1306]

For those who want to take a look, "Computer Organization and Design" by Hennessy and Patterson is a very common textbook on the subject (at least here in Italy). I found reading it to be a very, very instructive experience.

Its version of 32-bit MIPS is so simple, its whole instruction set fit in a 2-side cheatsheet (the famous "green sheet"). The design of the CPU is quite easy too. Given an instruction and its binary representation, it is almost straightforward to see how each bit contributes to the computation (setting the correct ALU operation, retrieving a value from the correct register, etc.).