If it is not there the data is retrieved from the main memory and a copy of it is placed in the cache block. And whenever a processor requires a data block it first checks it in its own cache memory. If we talk about the cache memory it is subdivided into a number of blocks. But before getting into the protocols we will discuss some terminologies associated to cache coherence problem. Well, this cache coherence problem can be sorted using the protocols discussed below. The figure below shows the cache coherence problem in a multiprocessing environment. And this problem is the cache coherence problem. But, the main memory and other processors’ cache will have the old copy of the shared memory block X. As the processor P1 will have the modified copy of the shared memory block i.e. In case, the processor P1 modifies the copy of shared memory block X present in its cache. The figure below shows how processors P1, P3 & Pn have the copy of shared data block X of main memory in their caches. Processors may share the same data block by keeping a copy of this data block in their cache. Now, keeping a common cache for all the processors will enhance the size of the cache thereby slowing down the performance of the system.įor better performance, each processor implements its own cache. In a multiprocessor environment, all the processors in the system share the main memory via a bus. Content: Cache Coherence in Computer Architecture In this section, we will discuss the cache coherence problem and the protocol for resolving the cache coherence problem.
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