“Virtual” caches

• Virtually addressed, virtually tagged caches

  • Synonym problem (2 virtual addresses corresponding to the same physical address).
  • Can be handled by software (disallow it) or by hardware with “pointers”
  • Use of PID’s to only partially flush the cache

• Virtually addressed, physically tagged

  • Easy and usually done for small L1, i.e., capacity < (page * ass.)
  • Can be done for larger caches if O.S. does a form of page coloring such that “index” is the same for synonyms
  • Can also be done more generally (complicated but can be elegant)

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