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Shared Memory Synchronization
Snoopy Bus Protocols
Cache consistency by bus watching mechanism
Each cache watches bus for write operations
Write through: forward write immediately to memory
Write-invalidate: cache copies are invalidated.
Write-update: cache copies are updated.
Disadvantage: high bus traffic.
Copy back: write modified cache line only back if
Line needs to be replaced, or
Another processor reads data.
See additional slides.
Last modification: November 15, 1996