GATE Computer Science (CS) 2017 Shift 2 Solved Paper

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Question : 55 of 65
 
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The read access times and the hit ratios for different caches in a memory hierarchy are as given below:
Cache
Read access time (in nanoseconds)
Hit ratio
I-cache
2
0.8
D-cache
2
0.9
L2-cache
8
0.9

The read access time of main memory is 90 nanoseconds. Assume that the caches use the referred-word-first read policy and the write back policy. Assume that all the caches are direct mapped caches. Assume that the dirty bit is always 0 for all the blocks in the caches. In execution of a program, 60% of memory reads are for instruction fetch and 40% are for memory operand fetch. The average read access time in nanoseconds (up to 2 decimal places) is ______.
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