Write Policy

A write policy determines how the cache deals with a write cycle. The 2 common write policies areWrite-Throughand Write-Back. In Write-Back policy, the cache behave like a buffer. That is, when the processor begins a write cycle the cache receives the data and end the cycle.  The cache then writes the data  back  to  main  memory  when  the  system  bus  is  available. This method provides the higher performance by let the processor to continue its job when main memory is updated at a later time. However, controlling writes of  themain memory increase the cache's complexity and price. The second method is the Write-Through policy. The processor writes through the cache to main memory. The cache can update its contents, however the write cycle does not end till the data is stored into main memory. This method is less complicated and therefore less expensive to implement. The efficiency with a Write-Through policy is lower since the processor might wait for main memory to accept the data.