Memory Hierarchy 2

1
Memory Hierarchy 2
2
Exploiting Spatial Locality - Larger than one
work block size
3
Miss Rate vs. Block Size
4
(No Transcript)
5
Cache Organization Spectrum
6
Cache Organization Example
7
Implementation of Set Associative Cache
8
Cache Block Replacement Policy

• Direct-mapped Caches
• No replacement policy is needed since each
  memory block can be placed in only one cache
  block
• N-way set-associative Caches
• Each memory block can be placed in any of the n
  cache blocks in the mapped set
• Least Recently Used (LRU) replacement policy is
  typically used to select a block to be replaced
  among the blocks in the mapped set
• LRU replaces the block that has not been used
  for the longest time

9
(No Transcript)
10
(No Transcript)
11
(No Transcript)
12
(No Transcript)
13
(No Transcript)
14
(No Transcript)
15
(No Transcript)
16
Miss Rate vs. Set Associativity
17
Reducing the Miss Penalty - Multilevel Caches

• L1 (first-level) cache Optimized for fast hit
  time
• L2 (second-level) cache Optimized for high hit
  rate
• Important concern Inclusion property

18
Various Main Memory Options
19
(No Transcript)
20
Summary

• Memory hierarchies attempt to optimize memory
  cost and performance
• involves trade-offs among size, speed, and cost
• provides an illusion of an access time of the
  highest-level memory with the size and cost of
  the lowest-level memory (thanks to temporal and
  spatial localities)
• Cache memory is an instance of a memory hierarchy
• exploits both temporal and spatial localities
• direct-mapped caches are simple and fast but
  have higher miss rates
• set-associative caches have lower miss rates but
  are complex and slow
• multilevel caches are becoming increasingly
  popular