Computing The CPU

Computing MODULE 6 - THE CPU

What is the CPU?

The Central Processing Unit (CPU) executes instructions, performs calculations, and processes data from software apps and hardware.

CPU Cycle

  • A CPU cycle is the basic unit of time for operations, measured in Hertz (Hz), with modern CPUs operating in Gigahertz (GHz).

  • The system clock synchronizes CPU operations, where each tick represents a CPU cycle.

Instruction Processing

  • Instruction processing may require multiple CPU cycles (e.g., fetching, decoding, executing).

  • Pipelining optimizes efficiency by overlapping instruction execution.

Basic Components of the CPU

  1. Control Unit (CU): Manages operations, fetches, and decodes instructions.

  2. Arithmetic Logic Unit (ALU): Performs arithmetic and logical operations.

  3. Accumulator: Temporarily stores results of calculations.

Single Core vs. Multi-Core CPU

  • Single-Core: Executes tasks sequentially.

  • Multi-Core: Executes tasks in parallel, enhancing multitasking.

Opcodes and Operands

  • Opcode: The instruction code specifying operations (e.g., ADD).

  • Operand: The data or memory location the opcode acts upon.

Architecture & Address Space

  • Includes CPU, memory, and I/O components. Address space is determined by address bus width.

Summary of Fetch Execute Cycle

  • Fetch: Retrieves the instruction from memory using the Program Counter (PC).

  • Decode: Control Unit (CU) decodes the instruction and identifies operands.

  • Execute: ALU performs the operation using the operands based on control signals from the CU.

  • Store: Writes the results back to memory or registers as needed.

Components Summary

  • Address Bus: Carries addresses (unidirectional).

  • Data Bus: Transfers data (bidirectional).

  • Control Bus: Sends control signals (bidirectional).