Clock and NRU Combine Clock with Not-recently-used (NRU) Used (u) and modified (m) bits 1 st round: look for page with u=0 and m=0, do not modify u 2 nd round: look for page with u=0 and m=1, clear u 3 rd round: repeat 1 st round, then 2 nd round Saves on writes to hard disk
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