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Page tables are stored in memory , which has access time of 100 ns. The TLB holding 8 page table entries, has an access time of 10 ns. 
Using execution of process , it is found that 85 % of the time, a required page table entry exist in TLB and only 2 % of the total references causes page fault. Page replacement time is 2 ms . Calculate the effective memory access time , assuming page memory access requires 2 memory accesses and TLB requires one memory access. 

A) 38120 ns B) 40000 ns C) 40120 ns D) None 
==={{Template:Author|Arjun Suresh|{{arjunweb}} }}===


Let S be average memory access time. 
<!--
 S = Time when TLB hits (85 %)+ Time when TLB misses (15%) + Time for page faults (2% of total memory accesses)
 = 0.85 * (10+100)
 +0.15 * (10+100+200 +  2,000,000*2/100)
 = 0.85 * 110
+0.15(80620)
 = 40140
-->
{{Template:FBD}}

[[Category: Non-GATE Questions from OS]]