Applied Test Series

Question

An operating system implements a single level paging. This system uses Translation Lookaside Buffer (TLB) and Physical Address Cache (PAC) as well. TLB has a hit ratio 90%. PAC has a miss ratio of 20%. Main memory access time, TLB access time and PAC access time are 100 ns, 20 ns and 40 ns respectively. Assuming that all the pages of the process are in main memory, the effective memory access time is ______ (ns).

 

Answer 1

Effective memory access time (or)

EMAT = 90/100 [ 20 + (80/100)*40

(20/100) * (40 + 100)]

     + 10/100 [ 20 + 100 + (80/100)*40

                  + (20/100) * (40 + 100)]

  = 0.9 [ 20 + 32 + 28]

0.1 [ 120 + 32 + 28 ]

  = 0.9 [80] + 0.1 [ 180 ]

 = 72 + 18

 = 90 ns