Write Hit Policies:

• Write through

o   Update next level on every write

o   Cache is always clean

o   A lots of traffic to next level (mostly write)

• Write back

o   Write to cache and mark block dirty

o   Update primary memory to eviction

o   Less traffic to next ,but more complicated eviction and coherence

• Reservation problem

o   Reads use directly and data array at the same time

o   Write use directory first then data array

o   How to we pipeline to permit one read or write per cycle?