I/O and caches (a first look at cache coherence)

• I/O data passes through the cache on its way from/to memory

  • No coherency problem but contention for cache access

• I/O interacts directly with main memory

• Case 1: Software solution

  • Output: (1) Write-through cache. No problem ;(2)Write back cache purge the cache via O.S. interaction
  • Input (WT and WB). Use a non-cacheable buffer space. Then after inputmake the buffer cacheable

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