The next three columns represent the actual bits in

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Unformatted text preview: nger access times, and thus tend to use larger block sizes in order to amortize these longer access times. 302 CHAPTER 6. THE MEMORY HIERARCHY Cache Hits When a program needs a particular data object from level · ½, it first looks for in one of the blocks currently stored at level . If happens to be cached at level , then we have what is called a cache hit. The program reads directly from level , which by the nature of the memory hierarchy is faster than reading from level · ½. For example, a program with good temporal locality might read a data object from block 14, resulting in a cache hit from level . Cache Misses If, on the other hand, the data object is not cached at level , then we have what is called a cache miss. When there is a miss, the cache at level fetches the block containing from the cache at level · ½, possibly overwriting an existing block if the level cache is already full. This process of overwriting an existing block is known as replacing or evicting the block. The block that...
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