Write Policies

Diagrams/writes.eps

Write-Through

• Data is written to the block in the cache and the block in the lower-level memory

• Cycle time is that of memory

• Memory is always coherent

Write-Back

• Data is only written to the cache

• Modified blocks are written to memory only when replaced

• Cycle time of a hit is that of the cache

• Uses dirty bits to mark blocks which need to be written back when replaced