Lower-level Protocol Choices

• BusRd observed in M state: what transitition to make?

  • M ----> I
  • M ----> S
  • Depends on expectations of access patterns

• How does memory know whether or not to supply data on BusRd?

• Problem: Read/Write is 2 bus xactions, even if no sharing

  • BusRd (I->S) followed by BusRdX or BusUpgr (S->M)
  • What happens on sequential programs?

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