The primary objective of this experiment is to provide students with comprehensive understanding of Reorder Buffer (ROB) mechanisms and Out-of-Order Execution in modern superscalar processors.

Learning Objectives

By the end of this experiment, students will be able to:

1. Understand Reorder Buffer Architecture

   • Explain the structure and organization of reorder buffers
   • Identify the key components: head pointer, tail pointer, and ROB entries
   • Understand how ROB enables speculative execution with precise interrupts

2. Analyze Out-of-Order Execution

   • Comprehend the differences between program order and execution order
   • Understand how instructions can execute out-of-order while maintaining correctness
   • Analyze the benefits and challenges of out-of-order execution

3. Master Register Renaming

   • Understand how ROB entries serve as temporary register names
   • Analyze how register renaming eliminates false dependencies (WAR, WAW)
   • Study the interaction between Register Alias Table (RAT) and ROB

4. Understand Precise Interrupt Handling

   • Learn how ROB enables precise interrupts in out-of-order processors
   • Understand the commit process and its role in maintaining precise state
   • Analyze exception handling and pipeline recovery mechanisms

5. Evaluate Performance Impact

   • Measure the performance benefits of out-of-order execution
   • Understand factors affecting ROB efficiency and utilization
   • Analyze the trade-offs between hardware complexity and performance gains

6. Apply Theoretical Knowledge

   • Simulate various instruction sequences and dependency patterns
   • Observe how different workloads utilize ROB resources
   • Experiment with exception scenarios and recovery procedures

Key Concepts Covered

• Reorder Buffer Structure: Entry allocation, state tracking, and management
• Instruction Lifecycle: Issue → Execute → Complete → Commit phases
• Dependency Handling: True dependencies vs. false dependencies
• Exception Handling: Precise interrupts and pipeline flushing
• Performance Metrics: ROB utilization, commit rate, and CPI analysis
• Modern Processor Design: Real-world applications in contemporary CPUs

Practical Skills Developed

• Simulation Analysis: Interpreting ROB state changes and instruction flow
• Performance Evaluation: Measuring and analyzing execution efficiency
• Problem Solving: Understanding complex processor behaviors and optimizations
• System Design: Appreciating the engineering trade-offs in processor architecture

This experiment bridges theoretical computer architecture concepts with practical implementation details, providing students with essential knowledge for understanding modern high-performance processors.