2 votes 2 votes Consider a memory system consists of a single external cache with an access time of 20ns and a hit rate of 0.92, and a main memory with an access time of 60ns. Now we add virtual memory to the system. The TLB is implemented internal to the processor chip and takes 2ns to do a translation on a TLB hit. The TLB hit ratio is 98%, the segment table hit ratio is 100% and the page table hit ratio is 50%. What is the effective memory access time of the system with virtual memory? 27.3ns 28.2ns 29ns 29.44ns Anirban Biswas asked Jan 8, 2017 Anirban Biswas 2.3k views answer comment Share Follow See 1 comment See all 1 1 comment reply arun yadav commented Sep 12, 2020 reply Follow Share WHAT IS SEGMENT TABLE HIT RATIO AND PAGE TABLE HIT RATIO? WHAT IS THE USE OF THIS DATA IN THESE QUESTIONS 0 votes 0 votes Please log in or register to add a comment.
7 votes 7 votes Time to access TLB = 2 ns. Main memory access time = 60ns. External cache access time = 20 ns. $t_{eff}=t_{TLB}+(1-hit_{TLB})\;(t_{seg}+t_{page})+ t_{cache}+(1-hit_{cache})\;t_{RAM}$ $=2+0.02(20+20+0.5*60) + 20 + 0.08*60 = 28.2$ ns. visakh r answered Nov 4, 2016 visakh r comment Share Follow See all 15 Comments See all 15 15 Comments reply Show 12 previous comments Akriti sood commented Nov 17, 2016 reply Follow Share @arjun sir,this is the only information that is provided in question,i think other 50% means that page entry for that page is not there in page table and hence the page is not present in main memory and have to fetch from secondary memory 0 votes 0 votes Akriti sood commented Nov 17, 2016 reply Follow Share @visakh,can you tell what is meant by page table hit ratio here??does it mean that 50% of the time page table is present in cache and other 50%,it is present in main memory?? 0 votes 0 votes SeemaTanwar commented Dec 26, 2017 reply Follow Share teff=tTLB+(1−hitTLB)(tseg+tpage)+tcache+(1−hitcache)tRAM =2+0.02(20+20+0.5∗60)+20+0.08∗60=28.2 ns. how you equated tseg+tpage as 20+20+.5*60 ? 0 votes 0 votes Please log in or register to add a comment.