Aug2016 cs Q51

0. An operating system supports a paged virtual memory, using a central processor with a cycle time of one microsecond. It costs an additional one microsecond to access a page other than the current one. Pages have 1000 words, and the paging device is a drum that rotates at 3000 revolutions per minute and transfers one million words per second. Further, one percent of all instructions executed accessed a page other than the current page. The instruction that accessed another page, 80% accessed a page already in memory and when a new page was required, the replaced page was modified 50% of the time. What is the effective access time on this system, assuming that the system is running only one process and the processor is idle during drum transfers?

Answer
Comment
Array

Option : B
Explanation :
Effective access time = 0.99 * (1 µs) + 0.8 *.02 µs + 0.001 * ( 10000 µs + 1000 µs) + 0.001 * (20000 µs + 2000 µs) = (0.99 +0.016+22.0+11.0) µs = 34 µs So, option (B) is correct.

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