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Unformatted text preview: have a hit time of one clock cycle. 6.4. CACHE MEMORIES 321 Impact of Block Size Large blocks are a mixed blessing. On the one hand, larger blocks can help increase the hit rate by exploiting any spatial locality that might exist in a program. However, for a given cache size, larger blocks imply a smaller number of cache lines, which can hurt the hit rate in programs with more temporal locality than spatial locality. Larger blocks also have a negative impact on the miss penalty, since larger blocks cause larger transfer times. Modern systems usually compromise with cache blocks that contain 4 to 8 words. Impact of Associativity The issue here is the impact of the choice of the parameter , the number of cache lines per set. The advantage of higher associativity (i.e., larger values of ) is that it decreases the vulnerability of the cache to thrashing due to conflict misses. However, higher associativity comes at a significant cost. Higher associativity is expensive to implement and hard to make fast. It requires more tag bits per line, ad...
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This note was uploaded on 09/02/2010 for the course ELECTRICAL 360 taught by Professor Schultz during the Spring '10 term at BYU.

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