Method 1:
- We are having TLB lookup irrespective of a miss or hit
- We are having access to the physical memory irrespective of a miss or hit
- Extra time in case of a hit = 0ms
- Extra time in case of a miss = 80ms
Total time = TLB lookup time + Memory access time + 0.4*(Extra times in case of miss) + 0.6*(Extra time in case of hit)
Total time = 10 + 80 + 0.4*80 + 0.6*0 = 122ms
Method 2:
Total time = (Virtual address to physical address conversion time) + (Memory access time)
-- In case of TLB hit :
Virtual address to physical address conversion time = TLB lookup time = 10ms
-- In case of TLB miss :
Virtual address to physical address conversion time = TLB lookup time + Access physical memory of page table
Virtual address to physical address conversion time = 10 + 80 = 90ms
-- Average Virtual address to physical address conversion time
Virtual address to physical address conversion time = 0.6*(In case of TLB hit) + 0.4*(In case of TLB miss)
Virtual address to physical address conversion time = 0.6*10 + 0.4*90 = 42ms
-- Total time
Total time = (Virtual address to physical address conversion time) + (Memory access time) = 42ms + 80ms = 122ms