A Directory Entry
•Directory entries don’t usually keep cache state
•Use a P-length bit-vector to tell in which processors the block is present … presence bit
•Clean/dirty bit implies exactly 1 presence bit on
•Sufficient?
•Determine who has valid copy for read-miss
•Determine who has copies to be invalidated
Dirty
P0
P1
P2
1
P3
P4
1
P5
P6
P7
Presence Bits