3/26/2023 0 Comments Associative cache vs direct mapped![]() ![]() How many memory addresses will be mapped to how many lines in the cache? My image has 8 to 4. However, I can't figure out how many lines there should be (16 words, line size 4 words). I attached a picture with a cache that has 8 memory addresses mapped to 4 lines. The mapping is arbitrary but for the context of H&P assume that the. Given any address, it is easy to identify the single entry in. Direct-Mapped Cache is simplier (requires just one comparator and one multiplexer), as a result is cheaper and works faster. I don't expect a full answer but an indication on how to draft the direct mapped cache and come up with a sequence would be greatly appreciated. A direct mapped cache of size M blocks maps memory addresses directly into cache blocks. These are two different ways of organizing a cache (another one would be n-way set associative, which combines both, and most often used in real world CPU). ![]() If we have 16 words, 4 per line it would that would mean 4 total rows. Number of lines would be cache capacity / line size = ? / 2^4 Tag represents the unique identifier for that (A direct-mapped cache is one-way set-associative and a fully associative cache with m cache lines is m-way set-associative.) Many processor caches in today's designs are either direct-mapped, two-way set-associative, or four-way set-associative. Word are least significant bits which represent the address from main memory Cache structure: The range of caches from direct-mapped to fully associative is a continuum of levels of set associativity. LRU replacement - Oldest Used is replaced.MIPS uses Fetch, Decode, Execute, Encode, Memory (this might be irrelevant here).Direct Mapped Cache means that a block of memory is mapped directly to line of cache.Assume that the cache is word addressed, i.e., the low two bits of the address are always 0.Ĭome up with a sequence of addresses for a MIPS processor for which a direct-mapped cache of size 16 words, line size 4 words, outperforms a fully-associative cache with the same line size, using LRU replacement. Propose you have a cache with a line size of L 32-bit words, S number of sets, W ways, and addresses are made up of A bits. Trying to solve this problem where direct cache would outperform associative: ![]()
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