Computer architectureLesson 1 of 1 in the course Memory hierarchy

CPU Cache Organization, Policies, Addressing, and Hierarchies

5 flashcards · 5 quiz questions · 5 match pairs · 4 fill-in sentences · English

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Summary

This lesson introduces CPU caches, explains why they improve performance, and compares the memory technologies used to build them.

A CPU cache is a small, fast hardware memory located close to a processor core. It stores copies of data from main memory that the processor is likely to use again. When the CPU can obtain needed data from the cache, it avoids a slower trip to main memory.

All flashcards

What is a write-back cache?
A cache that delays writing modified data to main memory until eviction or another required write-back.
What is a homonym in cache addressing?
The same virtual address referring to different physical addresses, often in different processes.
What is a synonym in cache addressing?
Different virtual addresses referring to the same physical address.
What is a victim cache?
A small cache that holds lines recently evicted from a main cache.
What is a cache stall?
A period when the processor waits because requested data is not yet available.

Quiz questions

  1. What does a cache's least-recently-used replacement policy select for eviction?Answer: The line that has gone the longest without being accessed.
  2. In a write-back cache, what happens to a modified line when it is evicted?Answer: The dirty line is written to main memory.
  3. What is a central purpose of cache-coherence protocols in a multicore system?Answer: To coordinate cached copies so processors do not use inconsistent data.
  4. How does a VIPT cache begin its lookup before address translation finishes?Answer: It uses virtual-address bits to select a set, then checks a physical tag.
  5. What is a common trade-off when cache associativity is increased?Answer: Fewer conflict misses may come at the cost of more hardware and access complexity.

Based on the Wikipedia article CPU cache, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.

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