Lecture 10

# On part 2 program opmizaons that consider caches cache

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Unformatted text preview: n binary is 00...0110000 011 0011. (m-k-4) bits k bits Tag Index m-bit Address k=3 4-bit Block Offset k=2 k=1 1-way associativity 8 sets, 1 block each 2-way associativity 4 sets, 2 blocks each 4-way associativity 2 sets, 4 blocks each Set 0 1 2 3 4 5 6 7 Set Set 0 0 1 2 1 3 Cache Organiza?on University of Washington Block replacement       Any empty block in the correct set may be used for storing data. If there are no empty blocks, which one should we replace? Replace something, of course, but what?   Caches typically use something close to least-recently-used 1-way associativity 8 sets, 1 block each 2-way associativity 4 sets, 2 blocks each 4-way associativity 2 sets, 4 blocks each Set 0 1 2 3 4 5 6 7 Set Set 0 0 1 2 1 3 Cache Organiza?on University of Washington Another puzzle.         What can you infer from this: Cache starts empty Access (addr, hit/miss) stream (10, miss); (12, miss); (10, miss) Cache Organiza?on University of Washington Memory and Caches           Cache basics Principle of locality Memory hierarchies Cache organiza?on (part 2) Program op?miza?ons that consider caches Cache Organiza?on University of Washington General Cache Organiza?on (S, E, B) E = 2e lines per set set line S = 2s sets v valid bit tag 012 B ­1 cache size: S x E x B data bytes B = 2b bytes of data per cache line (the data block) Cache Organiza?on University of Washington Cache Read E = 2e lines per set • Locate set • Check if any line in set has matching tag • Yes + line valid: hit • Locate data star4ng at oﬀset Address of byte in memory: t bits tag S = 2s sets s bits b bits set block index oﬀset data begins at this oﬀset v valid bit tag 012 B ­1 B = 2b bytes of data per cache line (the data block) Cache Organiza?on University of Washington Example: Direct ­Mapped Cache (E = 1) Direct ­mapped: One line per set Assume: cache block si...
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## This document was uploaded on 04/04/2014.

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