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School of Computer Science & Engineering
University of New South Wales
 Advanced Operating Systems 
 COMP9242 2002/S2 

Cache replacement policy

• Indexing (via virtual or physical address) points to line set.

• If all lines of set are valid must replace an existing one.

• Replacement strategy must be simple as it's all done in hardware.

• Dirty bit is used to determine whether a line must be flushed back to memory before invalidation.

• Typical policies:
  • LRU (or approximation)
  • FIFO
  • random