Cache-Memory closed

Question

If it takes 50ns to search associative registers and also about 100ns to get access to main memory then find out the % of slowdown in memory access time?(Given hit ratio 90%)-

A)60

B)75

C)20

D)90

Comments

The question is not clear. It is asking percentage of slowdown of memory compared to what?

Answer 1

considering when hit ratio is 90%

average memory access time =0.9(50)+0.1(100+50)=60

comparing it with when hit ratio is 100%:

memory access time is 50

slow down =(60-50)/50=0.2

0.2 * 100=20%

Comments

yes i also got 20% but the answer given was 60.Perhaps they might have marked it incorrectly.