Final Strategies in Caches:

• Cache write is more complicated than cache read because even if you
  have a hit, you have to decide if and when you write it back to main
  memory. This is of utmost importance in multiprocessor systems.
• Two main strategies are used:
  -1. Write-through
  a)All writes are passed to main memory immediately
  b)If there is a hit, the cache is updated to hold new value
  c)Processor slows down to main memory speed during write
  -2. Write-back
  a)Write operation updates the cache, but not main memory
  b)Cache remembers that it is different from main memory via a
  dirty bit
  c)It is written back to main memory only when the cache line is
  used by new data