A computer uses virtual memory implemented by paging. The TLB lookup
takes 50 ns and the update takes 100 ns. The PT lookup takes 2 µs and the
update takes 1 µs. Loading a word from main memory onto the CPU takes 5 µs
and loading a page from the disk into main memory takes 15 ms. The TLB hit
ratio is 0.5 and the main memory hit ratio is 0.2.
We define access time as the total time it takes to (1) find the referenced
word, (2) load it into the CPU, and (3) update the TLB and page tables if that
is necessary.
Answer the following questions:
(a) What is the average access time in the case of a TLB hit?
(b) What is the average access time in the case of a TLB miss and PT hit?
(c) What is the average access time if the case of a TLB miss and a PT miss?
(d) What is the average access time in general?
