ENGR 325 HOMEWORK #8 ANSWER KEY

5) Recall that we have two write policies and write allocation policies, and their combination can be implemented either in L1 or L2 cache. Assume the following choice for L1 and L2 caches: L1 L2 Write-through, non-write allocate Write-back, write allocate Describe the procedure of handling an L1 write-miss, considering the component involved and the possibility of replacing a dirty block. (P&H 5.4, §5.3, 5.8) SOLUTION: When an L1 write miss occurs, a cache block is not allocated in L1 for the block in question. L2 is written directly. Since L1 is a write-through cache, there are no issues with dirty blocks in L1. If there is an L2 cache hit, L2 is simply updated and the dirty bit set. If there is an L2 cache miss, a block must be allocated in L2 and the evicted block must be written back to main memory if it is dirty. 2. (10) Media applications that play audio or video files are part of a class of workloads called “streaming” workloads; i.e., they bring in large amounts of data but do not reuse much of it. Consider a video streaming workload that accesses a 512 kiB working set sequentially with the following address stream (P&H 5.5, §5.1, 5.4, 5.8, 5.13): 0, 2, 4, 6, 8, 10, 12, 14, 16, …