10. Answer the following questions about cache memory using a computer system wi

Question

10. Answer the following questions about cache memory using a computer system with the following characteristics: Total Memory Requests: 5000, Memory Requests Found in Cache 3500, Average Main Memory Access Time: 1000 nsec, and Average Cache Memory Access Time: 200 nsec. A. What is the Hit Ratio for the system? B. What is the Average Memory Access Time for the system? C. Explain why is the Average Cache Memory Access Time is a constant value in the Average Memory Access Time formula. Ratio value in the Average Memory Access Time formula Memory Access Time? D. Explain why is the Average Main Memory Access Time is dependent on the Hit E. What affect, if any, would doubling the available cache memory have on the Average

Explanation / Answer

Solution:

A)

Hit ratio = 3500/5000 = 0.7,

we can say that 70%

B)

Average memory access time = hit ratio * cache memory access time + miss ratio(1-hit ratio) * (cache memory access time + main memory access time)

so

AMAT = 0.7*200 + (0. * (200+1000))

= 140 ns

C)

Because there is cache will be accessed or not, but the main memory will be accessed only when the cache operation is a miss so to calculate the average memory access time we need to take care of both the cases.

D)

Because the hit ratio explains that how many times the data was accessed from the cache memory which also means that it tells how many times there was a miss and main memory was accessed.

E)

It depends whether the cache memory is enough to hold the frequent operations happening in the system, but the content which is not available in the cache memory will always be accessed from the main memory and kept as a frequent data in the cache for future but as another memory operation comes it will keep on changing depending on the algorithm which is used.

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