Show understanding of the four basic computer architectures

15.1 Processors, Parallel Processing and Virtual Machines

1️⃣ Von Neumann Architecture

Think of a Von Neumann machine as a single‑lane road 🚗 where both the instructions (the directions) and the data (the cars) share the same space. The CPU fetches an instruction, decodes it, and then executes it, all from the same memory. This is the classic design that most early computers used.

The cycle time for each instruction can be expressed as: $$T = \frac{1}{f}$$ where f is the clock frequency.

2️⃣ Harvard Architecture

Imagine a two‑lane highway 🛣️: one lane carries instructions and the other carries data. Because they are separate, the CPU can fetch an instruction and read/write data at the same time, speeding up execution. This is common in embedded systems like microcontrollers.

3️⃣ Modified Harvard Architecture

A hybrid approach 🎛️. It keeps separate instruction and data buses like Harvard, but allows the CPU to share a common memory for both. This gives the best of both worlds: faster access and flexibility.

4️⃣ MIMD (Multiple Instruction, Multiple Data) Architecture

Picture a team of workers 🧑‍💻🧑‍💻 each with their own tools. In MIMD, multiple processors run different instructions on different data sets simultaneously. This is the backbone of modern supercomputers and cloud servers.

Parallel Processing Basics

Parallel processing splits a big task into smaller pieces that run at the same time. Think of it like a relay race 🏃‍♂️🏃‍♀️: each runner (processor) covers a segment, and the baton (data) is passed along. The total time saved depends on how well the work is divided and how fast the processors are.

1. Identify independent tasks.
2. Assign tasks to processors.
3. Synchronise results.

Virtual Machines (VMs)

A VM is like a virtual room 🏠 inside a real building. It runs its own operating system and applications, but all of its resources (CPU, memory, storage) are provided by the host computer. VMs let you run multiple isolated environments on one physical machine, which is great for testing or running different software stacks.

Summary Table