1.1 Systems Architecture

Overview

Master the CPU’s role, its fetch–decode–execute cycle, registers, performance factors like clock speed and cache, and embedded systems.

Specification Breakdown

1.1a: The CPU

Role: Acts as the computer’s brain by processing instructions.
Fetch–Decode–Execute: Operates using this cycle to retrieve, interpret, and carry out commands.
ALU: Performs arithmetic operations (e.g., addition, subtraction) and logical operations (e.g., AND, OR).
CU: Directs the coordinated functioning of the ALU, registers, and memory, ensuring each instruction is processed correctly.
Registers: Provide ultra-fast temporary storage for data and instructions during processing.

1.1b: Registers & Fetch–Execute

Fetch: Retrieves the next instruction from memory using the Program Counter (PC).
Decode: The Control Unit deciphers the instruction to determine the required operations.
Execute: The ALU or dedicated hardware performs the instruction; the PC then updates to the next address.
Key Registers:
- PC: Points to the next instruction.
- MAR: Holds the memory address for data access.
- MDR: Temporarily stores data moving to/from memory.

1.2: CPU Performance

Cache: A small, high-speed memory close to the CPU to store frequently accessed data.
Clock Speed: Measured in GHz; a higher speed means more cycles per second but also more heat.
Cores: Multiple cores allow the CPU to process several tasks concurrently, improving overall performance.

1.3: Embedded Systems

Definition: Specialized computer systems integrated into larger devices to perform dedicated tasks.
Purpose: Provide real-time control and monitoring for devices (e.g., microwaves, dishwashers, sat navs).
Examples: Insulin pumps, automotive control systems, household appliances.

Visual Aid

CPU & Fetch–Execute Flow

Quick Quiz

Drag terms to match their meanings—prove your skills!

Exam Prep Quiz

1. What’s the purpose of the CPU? [2]

The CPU serves as the computer’s brain, executing instructions via the fetch–decode–execute cycle.

2. Describe the roles of the ALU and CU. [4]

The ALU performs arithmetic and logic operations, while the CU directs operations, managing data flow between the ALU, registers, and memory.

3. Explain the fetch–decode–execute cycle. [3]

The cycle involves fetching an instruction from memory, decoding it to determine the action, executing the operation, and updating the Program Counter for the next instruction.

4. How do cache, clock speed, and cores affect CPU performance? [4]

Cache stores frequently accessed data for rapid access; higher clock speeds increase processing cycles but generate more heat; multiple cores allow parallel processing, enhancing performance.

5. What is an embedded system? Provide two examples. [3]

An embedded system is a specialized computer within a device designed for specific control functions. Examples include insulin pumps and automotive control systems.