It is the technical drawings and functional description of all design requirements ( especially speeds and interconnections ) , it is how to design and implement various parts of a computer â '' focusing largely on the way by which the central processing unit ( CPU ) operates internally and how it accesses addresses in memory . It 's a blueprint and functional description of requirements and design implementations for the various parts of a computer , focusing largely on the way by which the central processing unit ( CPU ) performs internally and accesses addresses in memory .