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2 Answers

Best answer
3 votes
3 votes

Given,

Avg Memory Access time = (Hit in L1) * (L1 time) + (miss in L1 * Hit in L2) * (L1 time + L2 time) + (miss in L1 * miss in L2 * Hit in main memory) * (L1 time + L2 time + main memory time)

= (1-0.15) * 5 + (0.15 * (1 – 0.20)) * (10 + 5) + (0.15 * 0.20 * 1) * (85 + 10 + 5)

= 9.05ns

OR

Avg Memory Access time = L1 time + (miss in L1) * (L2 time) + (miss in L1) * (miss in L2) * Main memory access time

= 5 + 0.15 * 10 + 0.15 * 0.2 * 85

= 9.05 ns

Note: As the question is not mention which access method is used, we use the simultaneous method (By default)

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2 votes
2 votes
AMAT = Hit time + Miss rate * Miss penalty

⇒ AMAT = 5 + 0.15*(10 + 0.20*85) = 5 + 0.15*(10 + 17) = 5+ 0.15*27 = 9.05