Patterson, D.A., Hennesy, J.L.: Computer Organization and Design, 2nd edn. Direct mapping: In direct mapping a block has only one option to get placed in cache. The key can be the set/line value and the value can be a vector of pairs of tag and access counter. In: IEEE/ACM International Symposium on Microarchitecture (MICRO-30), pp. 1st step All steps Final answer Step 1/2 Heres some advice for implementing your cache simulator: Unordered Map: You can use an unorderedmap to store the cache data. Kin, J., Gupta, M., Mangione-Smith, W.H.: The Filter Cache: An Energy Efficient Memory Structure. In: 2 nd IEEE ICCSIT 2009, Beijing, China (2009) I am personally aware of MIPS and RISC-V versions. However, the book mainly describes Reduced Instruction Set Architectures (RISC). Any configuration in between is called an N-way set-associative. This visualization should get along well with Soumen's explanation in the accepted answer. In this case, the number of sets equals the number of blocks. In a set-associative, it indexes the set. Megalingam, R.K., Deepu, K.B., Joseph, I.P., Vikram, V.: Phased Set Associative Cache Design For Reduced Power Consumption. In a direct-mapped cache, the 'index' part of the address addresses the line. Which cache mapping function is least likely to thrash, i.e., it has the lowest. Hasegawa, A., et al.: SH3: High Code Density, Low Power. Direct mapping b.) Set associative mapping c.) Fully associative mapping. when evicting a line: if D0 (memory data is NOT stale), just set V0. Koji, I., Tohru, I., Kazuaki, M.: Way Predicting Set Associative Cache for High Performance and Low Energy Consumption. Fully associative: block can be anywhere in the cache Direct mapped: block can. In a direct mapped cache, there is only one comparison required by using a direct formula to find the effective cache address for mapping. In: 14th Annual International Symposium on Computer Architecture, SIGARCH Newsletter, June 1987, pp. In: Proceedings of Second International Symposium on High-Performance Computer Architecture, February 1996, pp. By sending to four lines per set, the number of sets is decreased to 128 sets needing 7 bits to recognize the set and twenty bits for the tag.Calder, B., Grunwald, D., Emer, J.: Predictive Sequential Associative Cache. from a direct-mapped cache to a 2-way set associative cache requires. This can leave 30 – 8 – 3 = 19 bits for the tag. Lets compare the memory performance of a server versus desktop versus mobile. In the instance of the cache having 512 lines, we can achieve 256 sets of two lines each, which would require eight bits from the memory address to recognize the set. In a direct mapping scheme, this can leave 30 – 9 – 3 = 18 bits for the tag.īy sending from direct mapping to set associative with a set size of two lines per set, the various sets achieved equals half the number of lines. The set-associative cache is somewhat slower, so the CPU designer must be careful that it doesn’t slow down the CPU’s cycle time too much. Because the mapping approach uses the memory address only like direct mapping does, the number of lines included in a set should be similar to an integer power of two, for example, two, four, eight, sixteen, etc.Įxample − Consider a cache with 2 9 = 512 lines, a block of memory contains 2 3 = 8 words, and the full memory space includes 2 30 = 1G words. The set-associative cache generally provides higher hit rates than the direct-mapped cache because conflicts between a small set of locations can be resolved within the cache. The diagram represents this arrangement using a sample cache that uses four lines to a set.Ī set-associative cache that includes k lines per set is known as a k way set-associative cache. However, the lines within each set are treated as a small fully associative cache where any block that can save in the set can be stored to any line inside the set. The sets are persistent using a direct mapping scheme. Set associative mapping combines direct mapping with fully associative mapping by arrangement lines of a cache into sets.
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