Assume a system uses 2-level paging and has a TLB hit ratio of 90%. It requires 15 nanoseconds to access the TLB, and 85 nanoseconds to access main memory. What is the effective memory access time in nanoseconds for this system?

The effective memory access time = 293.5 nanoseconds.

Explanation:

Given that:

TLB hit ratio = 90%

= 90/100

= 0.9

Require time to access TLB = 15 nanoseconds &

Time to access main Memory = 85 nanoseconds

The objective is to estimate the effective memory access time in nanoseconds for this system.

The effective memory access time = [TLB Hit ratio (main memory access time + required time to access TLB) + (2 * main memory access time) + required time to access TLB) * (2 - TLB hit ratio) ]

The effective memory access time = [0.9 (85 + 15) + (2 * (85) + 15) * (2 - 0.90)

The effective memory access time = 293.5 nanoseconds.