Learn: The Fetch-Decode-Execute Cycle

Welcome!Building on what you've already learned about why the CPU is essential, we'll now explore how it processes instructions using the Fetch-Decode-Execute Cycle.

What is the Fetch-Decode-Execute Cycle?The Fetch-Decode-Execute Cycle is the process the CPU uses to carry out instructions. It involves fetching an instruction from memory, decoding it to understand what to do, and then executing it. This cycle happens repeatedly and very quickly.

Step 1: FetchDuring the fetch step, the Program Counter (PC) provides the address of the instruction in memory. The CPU retrieves this instruction and stores it in the Memory Data Register (MDR).This step ensures the CPU knows what instruction to process next.

Step 2: DecodeIn the decode step, the CPU interprets the fetched instruction. The Control Unit (CU) is responsible for this task. It determines what operation the instruction requires, such as addition or storing data.

Step 3: ExecuteDuring the execute step, the CPU carries out the decoded instruction. This could involve calculations performed by the Arithmetic Logic Unit (ALU), storing data, or transferring data between registers.

Factors Affecting CPU PerformanceThree key factors affect how quickly the Fetch-Decode-Execute Cycle runs: clock speed (how fast instructions are processed), cache size (how much fast memory is available), and number of cores (how many instructions can be processed simultaneously).

Review Time!Great work! You've learned about the Fetch-Decode-Execute Cycle, its steps, and how CPU performance is affected. Let's test your understanding with a few final questions.