ECS 154A Lecture Notes - Lecture 18: Web Cache, Dirty Bit, Computer Memory
14 Jul 2016
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Lecture 18: caches: word = typically size of int, 32 bits now, addressable units: usually bytes, but can be words. 2a = number of addressable units, where a is bits in an address: unit of transfer = number of bits written out or read in to memory at a time. During the execution of a program, its memory references (both instruction and data) tend to cluster temporally. This will force some line in the cache to be replaced with the desired data: dirty = when a line contains updated data that differs from the corresponding main memory. The larger the cache, the more gates involved in addressing them, and slower. One solution is a victim cache that stores the most recently evicted lines. The victim cache is between the direct mapped cache and the next larger level of memory: associative = blocks can be placed in any line, with the tags containing the entire block number.
