Lower-level Protocol Choices

• Can shared-modified state be eliminated?

  • If update memory as well on BusUpd transactions (DEC Firefly)
  • Dragon protocol doesn’t (assumes DRAM memory slow to update)

• Should replacement of an Sc block be broadcast?

  • Would allow last copy to go to E state and not generate updates
  • Replacement bus transaction is not in critical path, later update may be

• Can local copy be updated on write hit before controller gets bus?

  • Can mess up serialization

• Coherence, consistency considerations much like write-through case

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