In contemporary multiprocessor systems, it is customary to have one or two levels of cache associated with each processor. This organization is essential to achieve reasonable performance. It does, however, create a problem known as the cache coherence problem. The essence of the problem is this: Multiple copies of the same data can exist in different caches simultaneously, and if processors are allowed to update their own copies freely, an inconsistent view of memory can result. Questions: a. What are the two common write policies for cache? b. Briefly survey various software and hardware approaches to the cache coherence problem. Explain the MESI (modified/exclusive/shared/invalid) protocol in detail for the cache coherence