Electronics Engineering (ELEX) Board Practice Exam

What is the name of the stage where the CPU fetches instructions from the instruction cache in superscalar architecture?

1. Decode stage

2. Execute stage

3. Prefetch stage

4. Write-back stage

The correct answer is: Prefetch stage

In superscalar architecture, the prefetch stage is crucial as it is responsible for fetching instructions from the instruction cache into the pipeline for execution. This is essential in ensuring that the CPU has a continuous flow of instructions to process, thus maximizing throughput and minimizing idle cycles. During the prefetch stage, the CPU accesses the instruction cache, where the most frequently used or anticipated instructions are stored for quick access. By retrieving instructions ahead of time, the architecture can mitigate potential delays caused by waiting for fetch operations, which is particularly important in a superscalar design where multiple execution units are employed. Multiple instructions can be fetched in parallel, enabling the system to capitalize on its ability to execute several instructions simultaneously. The prefetching mechanism enhances performance by predicting which instructions will be needed next and loading them before they are actually requested by the execution units. This proactive strategy is a hallmark of efficient CPU design in superscalar architectures, ensuring that the instruction pipeline remains well-fed with minimal stalls.