Fundamentals of Computer Architecture – CPU, Bus, Memory, Addressing

This article is a term explanation of fundamentals of computer architecture – including exam questions, core components, and tags.

In a Nutshell

Computer architecture describes the logical structure and functioning of a computer system. Central components are CPU, memory, bus systems, and addressing.

Compact Technical Description

The CPU (Central Processing Unit) is the computing unit of the computer and executes commands. It consists of:

• Control unit (coordinates command execution)
• Arithmetic unit / ALU (arithmetic-logical operations)
• Registers (very fast temporary storage)

Data and commands are transmitted between CPU, memory, and peripherals via a bus system:

• Data bus
• Address bus
• Control bus

Memory includes, among others:

• RAM (volatile, fast)
• ROM (non-volatile)
• Cache (very fast, close to the CPU)

Addressing specifies how memory cells are accessed (address space depends on architecture/bus width, e.g. 32 bit).

Exam-Relevant Key Points

• CPU as central processing unit (ALU + control unit)
• Bus system: address, data, control lines
• RAM vs. ROM
• Addressing in binary; address space depends on bit width (IHK-relevant)
• Memory access via addresses on the address bus
• Security aspect: faulty addresses/buffer overflows
• Performance: bus/memory architecture as bottleneck
• Documentation: architecture/addressing logic traceable

Core Components

1. CPU
2. Control unit
3. ALU
4. Register set
5. Bus system
6. Main memory (RAM/ROM)
7. Cache
8. Peripherals
9. Addressing scheme
10. Memory hierarchy

Simple Practical Example

32-bit system: 2^32 addresses = 4 GiB address space
Address 0x00000000 -> 1st memory cell
Address 0xFFFFFFFC -> last (aligned) memory location

Explanation: CPU addresses RAM via the address bus; data is transmitted via the data bus; control bus signals read/write operations.

Advantages and Disadvantages

Advantages

• Standardized structure enables universal programmability
• Modular design (CPU/memory/I/O) is expandable
• Scaling via bus width/address space possible

Disadvantages

• Bus bottlenecks with many accesses
• Limited address space with 32 bit
• Unprotected memory access can create security risks

Typical Exam Questions (with Short Answer)

1. Task of the CPU? Execute commands, process data, control system operations.
2. What types of buses are there? Address bus, data bus, control bus.
3. What does 32-bit addressing mean? Maximum 2^32 memory addresses directly addressable.
4. RAM vs. ROM? RAM volatile/writable; ROM non-volatile (mostly read-only).

Learning Strategy

1. Draw block diagram (CPU/BUS/memory).
2. Calculate address spaces for 16/32/64 bit.
3. Practice tasks on bus width/addressing.
4. Think through error patterns (overflow, wrong address) mentally.

Further Information

1. https://www.inf-schule.de/rechner/netze/architektur
2. https://www.elektronik-kompendium.de/sites/bau/0201211.htm