NRU Algorithms (Not
Recently Used)
• Reference bit
With each page associate a bit, initially = 0
When page is referenced bit set to 1
Replace the one which is 0 (if one exists).
• We do not know the order
• Second chance
Need reference bit
Clock replacement
If page to be replaced (in clock order) has reference
bit = 1 then:
• set reference bit 0
44
Fundamentals of Computer Architecture Powered by: Jirawan Charoensuk
• leave page in memory
• replace next page (in clock order), subject to same rules