Digital Design & Computer Architecture - Lecture 25: Prefetching (Spring 2022)
•February 18, 2026
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Why It Matters
Effective prefetching directly improves application throughput while preventing costly cache‑coherence conflicts, making it a critical lever for modern multicore and data‑center architectures.
Key Takeaways
- •Prefetching reduces cache miss rate and latency significantly.
- •Placement of prefetches across hierarchy levels impacts coordination complexity.
- •Aggressive prefetching can cause inter-core cache interference issues.
- •Software and hardware prefetchers must balance accuracy versus bandwidth.
- •Emerging memory technologies expand prefetching opportunities and challenges.
Summary
The penultimate lecture of the Spring 2022 Digital Design & Computer Architecture series focuses on prefetching – the proactive loading of data into cache or registers before it is demanded by the processor. The instructor emphasizes that prefetching is one of the most impactful techniques for alleviating memory‑hierarchy bottlenecks, especially as systems adopt deeper, heterogeneous memory stacks.
Key insights include how prefetching can cut both cache‑miss rates and miss‑latency by bringing blocks into the appropriate cache level ahead of time. The design space spans from L1 to main memory and even remote nodes, raising coordination challenges across levels. The lecture also covers software‑driven prefetching (e.g., browsers preloading likely links) and hardware mechanisms, noting that aggressive strategies may introduce inter‑core interference and bandwidth pressure.
The professor highlights concrete examples: a web browser predicting user clicks, distributed prefetches from remote memory nodes, and the subtle interplay with cache‑coherence protocols such as MESI. He warns that a prefetch triggered by one core can evict useful data for another, underscoring the need for intelligent prediction and throttling.
For system architects, the takeaway is clear: effective prefetching can unlock significant performance gains, but only if designers carefully balance prediction accuracy, placement, and coherence overhead. As multicore and emerging memory technologies (e.g., PCM, FeRAM) become mainstream, refined prefetch strategies will be essential to sustain scaling and latency targets.
Original Description
Digital Design and Computer Architecture, ETH Zürich, Spring 2022 (https://safari.ethz.ch/digitaltechnik/spring2022/)
Lecture 25: Prefetching and Virtual Memory
Lecturer: Professor Onur Mutlu (https://people.inf.ethz.ch/omutlu/)
Date: June 2, 2022
Lecture 25 Slides (pptx): https://safari.ethz.ch/digitaltechnik/spring2022/lib/exe/fetch.php?media=onur-digitaldesign_comparch-2022-lecture25-prefetching-afterlecture.pptx
Lecture 25 Slides (pdf): https://safari.ethz.ch/digitaltechnik/spring2022/lib/exe/fetch.php?media=onur-digitaldesign_comparch-2022-lecture25-prefetching-afterlecture.pdf
Recommended Reading:
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A Modern Primer on Processing in Memory
Intelligent Architectures for Intelligent Computing Systems
RowHammer: A Retrospective
Fundamentally Understanding and Solving RowHammer
RECOMMENDED LECTURE VIDEOS & PLAYLISTS:
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Computer Architecture Fall 2021 Lectures Playlist:
Digital Design and Computer Architecture Spring 2021 Livestream Lectures Playlist:
Featured Lectures:
Interview with Professor Onur Mutlu:
The Story of RowHammer Lecture:
Accelerating Genome Analysis Lecture:
Memory-Centric Computing Systems Tutorial at IEDM 2021:
Intelligent Architectures for Intelligent Machines Lecture:
Computer Architecture Fall 2020 Lectures Playlist:
Digital Design and Computer Architecture Spring 2020 Lectures Playlist:
Public Lectures by Onur Mutlu, Playlist:
Computer Architecture at Carnegie Mellon Spring 2015 Lectures Playlist:
Rethinking Memory System Design Lecture @stanfordonline :
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