Block Size Tradeoff

• In general, larger block size take advantage of spatial locality BUT:

  • Larger block size means larger miss penalty:
    • Takes longer time to fill up the block
  • If block size is too big relative to cache size, miss rate will go up
    • Too few cache blocks

• In gerneral, Average Access Time:

  • Hit Time x (1 - Miss Rate) + Miss Penalty x Miss Rate

Miss

Penalty

Block Size

Miss

Rate

Exploits Spatial Locality

Fewer blocks:

compromises

temporal locality

Average

Access

Time

Increased Miss Penalty

& Miss Rate

Block Size

Block Size

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