Q1. Illustrate the effect of permitting two entries in a page table to point to the similar page frame in the memory? Explain how this effect could be employed to reduce the amount of time required to copy a large of memory from one place to the other? What would be the result on one page if some of the bytes of other page are updated?
Q2. The operating system supports paged virtual memory, by using a central processor with a cycle time of 1 ms. Costs an additional 1 ms to access a page other than the existing one. Pages encompass 1000 words, and the paging device is a drum which rotates at 3000 revolutions per minute and transfers 1 million words per sec. The given statistical measurements were obtained from the system:
a) 1% of all instructions executed accessed a page other than the existing page.
b) Of the instructions which accessed the other page, 80% accessed a page already which was in memory.
c) If a new page was needed, the replaced page was modified 50 percent of the time.
Compute the efficient instruction time on this system, supposing that the system is running one process only and that the processor is idle throughout drum transfers.