Divergence between memory capacity and speed more pronounced
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Capacity increased by 1000x from 1980-95, speed only 2x
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Gigabit DRAM by c. 2000, but gap with processor speed much greater
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Larger memories are slower, while processors get faster
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Need to transfer more data in parallel
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Need deeper cache hierarchies
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How to organize caches?
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Parallelism increases effective size of each level of hierarchy, without increasing access time
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Parallelism and locality within memory systems too
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New designs fetch many bits within memory chip; follow with fast pipelined transfer across narrower interface
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Buffer caches most recently accessed data
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Disks too: Parallel disks plus caching
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