Computer Architecture

Introduction to Computer Architecture:

  • Computer architecture is the design and structure of computer systems, including hardware and system organization.

Components of Computer Architecture:

  1. Central Processing Unit (CPU):

    • The "brain" of the computer that executes instructions.
    • Comprises the control unit (CU) and the arithmetic logic unit (ALU).
  2. Memory Hierarchy:

    • Consists of various levels of storage, including registers, cache, RAM, and secondary storage (hard drives, SSDs).
    • Hierarchical arrangement for balancing speed and capacity.
  3. Input/Output (I/O) Systems:

    • Facilitates communication between the computer and external devices.
    • Includes interfaces, controllers, and devices like keyboards, monitors, and network cards.
  4. Bus System:

    • A communication system that connects various components, allowing data transfer.
    • Buses include the data bus, address bus, and control bus.

Computer Organization vs. Computer Architecture:

  • Computer Organization: Refers to how hardware components work together.
  • Computer Architecture: Concerns the structure and design of the computer system.

Instruction Set Architecture (ISA):

  • Defines the set of instructions a CPU can execute and its behavior.
  • Determines the interface between software and hardware.

Types of Computer Architectures:

  1. CISC (Complex Instruction Set Computer):

    • Emphasizes a large and complex instruction set.
    • Often characterized by microcode and variable-length instructions.
    • Examples: x86, Intel 80x86.
  2. RISC (Reduced Instruction Set Computer):

    • Features a simplified instruction set with uniform instruction format.
    • Strives for high performance by executing instructions quickly.
    • Examples: ARM, MIPS, PowerPC.
  3. VLIW (Very Long Instruction Word):

    • Parallel processing architecture that schedules multiple operations.
    • Compiler-intensive and used in specialized applications.

Memory Architecture:

  1. Von Neumann Architecture:

    • Classic architecture with a single memory for both data and instructions.
    • Most modern computers follow this design.
  2. Harvard Architecture:

    • Separates data and instruction memory.
    • Typically found in embedded systems and some specialized applications.


  • Technique that allows the CPU to overlap instruction fetch and execution to improve performance.

Superscalar Architecture:

  • Allows multiple instructions to be issued simultaneously, improving instruction throughput.

Parallel Processing:

  • The use of multiple processors or cores to perform tasks simultaneously.
  • Common in modern CPUs, GPUs, and high-performance computing.

Cache Memory:

  • High-speed memory used to store frequently accessed data and instructions.
  • Reduces the time it takes to access data from main memory.

Conclusion: Computer architecture is the foundation of computer systems, encompassing the CPU, memory hierarchy, I/O systems, and more. It defines how hardware components are organized and how they interact. Understanding the principles of computer architecture is essential for designing efficient and high-performance computer systems and writing optimized software.