In a paged memory management algorithm, the hit ratio is 70%. If it takes 30…
2014
In a paged memory management algorithm, the hit ratio is 70%. If it takes 30 nanoseconds to search Translation Look-aside Buffer (TLB) and 100 nanoseconds (ns) to access memory, the effective memory access time is
Answer: D. 160 ns — Given: TLB access = 30 ns, memory access = 100 ns, TLB hit ratio = 0.7. On a TLB hit: time = TLB + memory = 30 + 100 = 130 ns. On a TLB miss: must access page…
- A.
91 ns
- B.
69 ns
- C.
200 ns
- D.
160 ns
Attempted by 249 students.
Show answer & explanation
Correct answer: D
Given: TLB access = 30 ns, memory access = 100 ns, TLB hit ratio = 0.7.
On a TLB hit: time = TLB + memory = 30 + 100 = 130 ns.
On a TLB miss: must access page table (in memory) and then the data, so time = TLB + memory (page table) + memory (data) = 30 + 100 + 100 = 230 ns.
Effective memory access time = hit_ratio × time_on_hit + (1 − hit_ratio) × time_on_miss = 0.7 × 130 + 0.3 × 230.
Compute the terms: 0.7 × 130 = 91, 0.3 × 230 = 69.
Total = 91 + 69 = 160 ns.
Therefore the effective memory access time is 160 ns.