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Memory Systems Caching

Memory Systems Caching. Lecture 24 Digital Design and Computer Architecture Harris & Harris Morgan Kaufmann / Elsevier, 2007. The Memory Interface. The Ideal Memory System. Memory Hierarchy. Memory Performance. Hit: is found in that level of memory hierarchy

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Memory Systems Caching

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  1. Memory SystemsCaching Lecture 24 Digital Design and Computer Architecture Harris & Harris Morgan Kaufmann / Elsevier, 2007

  2. The Memory Interface

  3. The Ideal Memory System

  4. Memory Hierarchy

  5. Memory Performance • Hit: is found in that level of memory hierarchy • Miss: is not found (must go to the next level of memory hierarchy)

  6. Caches A safe place to hide things • What data is stored? • How is the data found? • What data is replaced?

  7. What data is stored?

  8. How is data found?

  9. Direct-Mapped Cache

  10. Direct-Mapped Cache Hardware

  11. Direct-Mapped Cache Performance # MIPS assembly code addi $t0, $0, 5 loop: beq $t0, $0, done lw $t1, 0x4($0) lw $t2, 0xC($0) lw $t3, 0x8($0) addi $t0, $t0, -1 j loop done:

  12. Direct-Mapped Cache Performance # MIPS assembly code addi $t0, $0, 5 loop: beq $t0, $0, done lw $t1, 0x4($0) lw $t2, 0x24($0) addi $t0, $t0, -1 j loop done:

  13. N-Way Set Associative Cache

  14. N-way Set Associative Performance # MIPS assembly code addi $t0, $0, 5 loop: beq $t0, $0, done lw $t1, 0x4($0) lw $t2, 0x24($0) addi $t0, $t0, -1 j loop done:

  15. Fully Associative Cache

  16. Spatial Locality?

  17. Increasing Cache Line Size

  18. Direct-Mapped Cache Performance # MIPS assembly code addi $t0, $0, 5 loop: beq $t0, $0, done lw $t1, 0x4($0) lw $t2, 0xC($0) lw $t3, 0x8($0) addi $t0, $t0, -1 j loop done:

  19. What data is replaced?

  20. LRU Replacement # MIPS assembly lw $t0, 0x04($0) lw $t1, 0x24($0) lw $t2, 0x54($0)

  21. Caching Summary • Temporal and spatial locality • LRU or pseudo-LRU replacement • Cache Parameters: • C = capacity • b = block size • B = # blocks = C/b • S = number of sets • N = # blocks in a set (# of ways)

  22. Next Time Virtual Memory

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