Method and apparatus for managing write back cache

A network services processor includes an input/output bridge that avoids unnecessary updates to memory when cache blocks storing processed packet data are no longer required. The input/output bridge monitors requests to free buffers in memory received from cores and IO units in the network services processor. Instead of writing the cache block back to the buffer in memory that will be freed, the input/output bridge issues don't write back commands to a cache controller to clear the dirty bit for the selected cache block, thus avoiding wasteful write-backs from cache to memory. After the dirty bit is cleared, the buffer in memory is freed, that is, made available for allocation to store data for another packet.