what is hit ratio?

Question

In a 2 level memory, if the level 1 memory is 5 times faster than level 2 and its access time is 10ns less than avg access time.Let the level 1 memory access time is 

20ns.

(a.)0.7
(b.)0.75
(c.)0.86
(d.)0.96

Answer 1

let level 1 access time t1 & level 2 t2...

then t2 = 5 t1----->  eq(1)

t1 = t_avg  - 10====>eq2

 t_avg  =   t1 + 10

t1 = 20 ns (given)

from eq1 we get,,,

t2 =100 ns

from eq2 we get,,,

 t_avg = 30ns

now for simultaneous memory organization..

 t_avg = H t1 + (1-H) t2

30 = H *20 + (1-H) *100

H = .875

Comments

It would be really helpful if you could tell where I went wrong instead of just down-voting the comment.

Thanks in advance.

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Shraddha u r right.

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So by default we have to rake simultaneos access and if the qurstuon contain hierarichal access then we have to consider hierarchical approach right?

Answer 2

Answer C