CS501 Assignment 1 Solution Fall 2017

Suppose we have a Processor XYZ with the following specifications:

  • Processor speed is 1 GHz.
  • It takes 2500 clock cycles to carry out a context switch followed by starting an Interrupt Service Routine (ISR).
  • To execute an ISR, 5000 cycles are required.
  • The device makes 100 interrupt requests per second.
  • Moreover when there are no interrupts, the processor polls for every 0.7 milli-sec and 300 cycles are required to poll an I/O device.

Students are required to calculate:

  1. No of cycles/sec the processor spends for handling I/O provided interrupts are used only.
  2. Percentage of CPU time used in interrupts handling.
  3. No of cycles/sec spent in I/O when polling is also used with interrupts.
  4. How frequently the processor polls so that it incurs the same overhead as interrupts.