Enhanced Second-Chance

• 2-bits, reference bit and modify bit

• (0,0) neither recently used nor modified

  • best page to replace

• (0,1) not recently used but modified

  • needs write-out

• (1,0) recently used but clean

  • probably used again soon

• (1,1) recently used and modified

  • used soon, needs write-out

• Circular queue in each class -- (Macintosh)

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