Architecture recap

Data must be collected automatically in a Programable Computer

Control signals need to be extracted from each instruction

These instructions are stored in a Instruction Register (IR)

Process of loading instructions need to be controlled

Harvard Architecture

All subsystems are separate and self contained

Many systems controlled by one system

Subsystems give feedback to the controller to allow for a response to an event

Problem

Loading programs is complex

Requires a-lot of redundant hardware

Von Neumann Architecture

Alternates between being a controller and a controlled system each clock cycle

Thus no or less redundant hardware

Controller (what does it do?)

Fetches

Loads IR

Controlled (what does it do?)

contents of IR determine next action

executes

Problem

2x as slow as harvard due to shared bus (Von Neumann bottle neck)

Modern solutions

Typically a mix between the two

Mainly Von Neumann with extra buses, special purpose memories and pipelining

Harvard is used within this main system, for subsystems and microprograms for complex instructions