A sample question for my upcoming Operating Systems exam is:

Under which circumstances would the clock variant [of the second-chance algorithm] be preferred over the standard second-chance algorithm and why.

I was under the impression that the clock variant is always preferred. Am I missing something? Are there specific circumstances (hardware-related perhaps) where the clock variant would be preferred? Equally, is the standard algorithm ever preferred?

A similar question was asked and answered here but it didn't mention any benefits

EDIT: A comment from @Wandering below led me to ask my lecturer for more clarification, and he is not referring to the two-handed clock variant.

  • $\begingroup$ Perhaps they are asking the difference between two-handed clock and standard second-chance? If that is the case then you should look for access patterns where LRU does particularly poorly. $\endgroup$ – Wandering Logic Apr 21 '15 at 12:33
  • $\begingroup$ @WanderingLogic I have asked my Operating Systems lecturer this exact question, but he responded by saying that no, the question is about the traditional clock variant; being an eccentric man, he won't answer my questions directly so I haven't managed to squeeze any more information out of him. Will update if I am able to clarify further. $\endgroup$ – AlexMTMorgan Apr 22 '15 at 9:40

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