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Meeting Summary: CS 315-02 Lecture/Lab (Fall 2025)

  • Date and Time: Nov 20, 2025, 02:54 PM Pacific Time (US and Canada)
  • Meeting ID: 868 6589 0521

Quick Recap

  • Greg reviewed diverse approaches to Project 6 and outlined remaining semester tasks: Lab 11 practice questions and the final project (Project 7).
  • He introduced key computer architecture concepts: multi-cycle processors and pipelining, using both theory and a laundry analogy to illustrate throughput.
  • He explained pipeline hazards (data and control) and current operational challenges.
  • He announced an extra-credit option to combine Projects 6 and 7 into a full pipeline version capable of passing all Project 6 tests.
  • He noted that Project 7 materials would be released soon.

Next Steps

  • Greg:
  • Release Lab 11 practice questions today (due next week).
  • Release Project 7 (final project) and starter code in the Project 7 GitHub repo by today or early tomorrow morning.
  • Provide Project 7 test questions and assembly code in the Project 7 repo.
  • Continue the lecture on pipelining on Tuesday.
  • Continue discussion of Project 7 and hazard mitigation techniques in Tuesday’s class.
  • Update attendance in Canvas and grant 5 free late days to the student discussed at the end of class.
  • Students:
  • If they completed novel/interesting work on Project 6 without interactive grading, contact Greg to schedule it.
  • Complete Lab 11 practice questions by next week (Thanksgiving week).
  • Begin Project 7 by modifying the provided pipeline processor to handle hazards (data dependencies and control hazards).
  • Optional/Extra Credit: Combine Projects 6 and 7 to produce a full pipeline version that passes all Project 6 tests.
  • Student (unnamed): Meet with Greg after class to resolve attendance/passport issues.

Summary

Project 6 and Final Review

  • Greg highlighted the variety and innovation in students’ approaches to Project 6, including incremental partitioning and circuit explanations.
  • He encouraged students to schedule interactive grading if they lacked sufficient work for full credit.
  • Remaining semester items include:
  • Lab 11 practice questions (due next week),
  • Continued lectures on pipelining,
  • Project 7 as the final project (due the last day of class).
  • Final exam coverage: approximately 75% post-midterm material and 25% pre-midterm, with some overlap across projects.
  • He introduced multi-cycle processors in contrast to single-cycle designs and set expectations that Project 7 will explore additional architectural complexity.

Understanding Processor Cycles and Pipelining

  • Single-cycle vs. multi-cycle:
  • Multi-cycle designs allow variable execution times and more efficient reuse of limited resources, especially relevant to earlier computer systems.
  • Pipelining:
  • Analogous to an assembly line: increases instruction throughput even if individual instruction latency may be slightly longer.
  • Illustrated with a simplified laundry example where tasks are divided into stages and performed concurrently by two people, assuming each step takes 30 minutes.

Pipelining Concepts in Laundry and Processors

  • Laundry analogy:
  • Breaking the process into stages reduces total time compared to serial completion.
  • Processor application:
  • Typical pipeline stages: Instruction Fetch (IF), Decode (ID), Execute (EX), Memory Access (MEM), Write Back (WB).
  • The theoretical speedup approaches the number of stages, but practical constraints prevent fully realizing the ideal.

Pipeline Hazards and Mitigation Strategies

  • Pipeline structure and operation were reviewed with emphasis on keeping the pipeline full for maximum throughput.
  • Hazard types:
  • Data hazards: arise from instruction dependencies.
  • Control hazards: occur when control-flow changes (e.g., branches/jumps) alter the instruction stream.
  • Current handling:
  • No-ops can be used to address data hazards in the provided baseline pipeline.
  • Upcoming work:
  • Students will implement hazard mitigation to eliminate no-ops where possible (e.g., forwarding/bypassing and control-hazard techniques).
  • Extra credit:
  • Combine Projects 6 and 7 to build a full pipeline version that passes all Project 6 tests.
  • Next discussion on Project 7 is scheduled for Tuesday, with materials and practice test questions to be provided soon.