Consider a paging system with the page table stored in memor

Consider a paging system with the page table stored in memory.

a. If a memory reference takes 250 nanoseconds, how long does a paged memory reference take?

b. If we add TLBs, and 80 percent of all page-table references are found in the TLBs, what is the effective memory reference time? (Assume that finding a page-table entry in the TLBs takes zero time, if the entry is there.)

Solution

answer a: 500 nanoseconds. 250 ns to access the page table plus 250 ns to access the word in memory.

answer b: 250 nanoseconds. 80% of the time it\'s 250 ns, and the other 20% of the time it\'s 500ns, so the equation is:

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