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