e Invalidating a Block with Sharers Requestor 1. Invalidate block a Requested by p Processor p Shared cache Private Cache Memory Directory 5. Acknowledge a 2. Invalidate A Directory sends invalidate messages to all sharers Processor Q Private Cache Directory receives acknowledge message for all invalidates and 3. Invalidate a clears their presence bits Directory sends acknowledge Processor r message to p, and changes state Private Cache of block a to modified 2021/22 计算机体系结构Invalidating a Block with Sharers 2021/2/2 计算机体系结构 16