Snoopy Design Choices

Processor

ld/st

Snoop (observed bus transaction)

State

Tag

Data

. . .

• Controller updates state of blocks in response to processor and snoop events and generates bus xactions

• Often have duplicate cache tags

• Snoopy protocol

  • set of states
  • state-transition diagram
  • actions

• Basic Choices

  • write-through vs. write-back
  • invalidate vs. update

Cache

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