Advanced Computer Architecture, Imperial College 2001
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Berkeley cache coherence protocol:
state transition diagram
•1. INVALID
•2. VALID: clean, potentially shared, unowned
•3. SHARED-DIRTY: modified, possibly shared, owned
•4. DIRTY: modified, only copy, owned
The Berkeley protocol is representative of how typical bus-based SMPs work
Q: What has to happen on a “Bus read miss”?