[COA] Cache write through in hierarchical design

Question

For hierarchical access and write-through,The average write time is given by: 

1. Twt=H×Tmemory+(1−H)×(Tcache+Tmemory)

2. Twt=Tmemory

Which one to refer in question?Can we ignore Tcache and use the second one? Please clarify?

Answer 1

write through : in this technique cpu performs simultaneous write operation in both cache memory and main memory. 

(T avg)_read  = H_{r *}T_c + (1-H_r)*(T_m+T_c) {here H_r :read hit }

and 

(T avg)_write  = H_{w *} T_w + (1-H_w)*(T_m+T_w)  {here H_w: write hit}

here T_w (word updation time) = max (word updation time in cache , word updation time in Main memory)

then

(T avg)_{write through} = frequency of read operation _* (T avg)read + frequency of read operation * (T avg)write

Comments

almost same answer like pawan 

https://gateoverflow.in/4775/average-cycle-write-through-cache-elaborate-concept-please

read Arjun's comments ..

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from the above link

hierarchial access and write through

Twrite = Tmemory

right?

thats what i infered

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or this?

t _{avg write}=Hc*TW+(1-Hc)(TM+TW)