In a two -level virtual memory, the memory access time for main memory, $${t_M} = {10^{ - 8}}\sec $$ and the memory access time for the secondary memory, tag $$ = {10^{ - 3}}.$$ What must be the hit ratio, $$H$$ such that the access efficiency is within $$80$$ percent of its maximum value?

State whether the following statement are TRUE or FALSE with reason. The data transfer between memory and $${\rm I}/O$$ devices using programmed $${\rm I}/O$$ is fasterthan interrrupt-driven $${\rm I}/O$$.

A certain moving arm disk-storage device has the following specifications:
Number of tracks per surface $$=4004$$
Track storage capacity $$=130030$$ bytes
Disk speed $$=3600$$ rpm
Average seek time $$=30$$ m secs.
Estimate the average latency the disk storage capacity and the data transfer rate.

Assuming the current disk cylinder to be $$50$$ and the sequence for the cylinders to be
$$1, 36, 49, 65, 53, 1, 2, 3, 20, 55, 16, 65$$ and $$78$$ find the sequences of servicing using
(i) shortest-seek time first $$(SSTF)$$
(ii) elevator disk scheduling polices.