Write Strategy
Write through simultaneously updates the cache and the lower level in the memory hierarchy on each write.
Write back only updates the cache copy until the block is replaced, at which point the next lower level of the hierarchy is updated.
Write through advantages --
- Read misses are cheaper due to not waiting for write. Easier to implement, though it needs a write buffer.
Write back advantages --
- Multiple writes to a block require only one memory write.
- Can utilize wider channel to lower level memory.
Write back is always needed between memory & disk.
- Dirty bit in page table determines if write back needed.