Effective Access Time

Suppose:

• TLB lookup takes 5 nano sec.
• Memory access time is 100 nano sec.
• Hit ratio (probability to find page number in TLB) is ?

• Effective Access Time = (5+100)* ? +( 5+100+100)*(1- ?)
  
  
  Suppose ? = 80% (for example, TLB size = 16)

EAT = 105*.8 + 205*.2 = 125 nano sec.



Suppose ? = 98% (for example, TLB size = 64)

EAT = 105*.98 + 205*.02 = 107 nano sec.

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