Basic Write-back Snoopy Cache Designs

• Write-back protocols are more complex than write-through because modified data remains in the cache

• Introduce more cache states

  • Modified, or dirty, the value differs from memory
  • Exclusive, no other cache has this value

• We consider three

  • MSI, an invalidation protocol
  • MESI, an invalidation protocol
  • Dragon, an update protocol

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