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Wednesday 14 March 2012

Advance Computer Architecture-CS501 ASSIGNMENT 3 SOLUTION


Assignment No. 03 sOLUTION
Semester Spring 2011
Advance Computer Architecture-CS501

Total Marks: 15

Due Date: 09/06/2011

Objective:
To learn and understand basic concepts of I/O and polling loop.

Instructions:
Please read the following instructions carefully before solving & submitting assignment:
Assignment should be in your own wordings not copied from net, handouts or books.
It should be clear that your assignment will not get any credit (zero marks) if:

o   The assignment is submitted after due date.
o   The submitted assignment does not open or file corrupt.
o   The assignment is copied (from other student or copy from handouts or internet).
o   Student ID is not mentioned in the assignment File or name of file is other than student ID.

For any query about the assignment, contact at cs501@vu.edu.pk

GOOD LUCK
Question No 1
Marks = 10 

Let us have a 20MIPS processor, you have to calculate the percentage of time it spends in busy wait loop of a 75-character line printer, when it takes 2 msec to print a character and a total of 665 instructions require to be executed to print a 75 character line.

Suppose that two instructions are executed in the polling loop.

Solution:

Out of the total 665 instructions executed to print a line, 75x2=150 is required for polling. For a 20MIPS processor, the execution of the remaining 515 instructions takes 515/ (20x106) = 25.75µsec. Since the printing of 75 characters takes 150ms, (150-0.02575) =149.97msec is spent in the polling loop before the next 75 characters can be printed. This is 149.97/150=99.98% of the total time.

Question No 2
Marks=5     

Let us assume that a program takes 400 seconds of elapsed time to execute.  Out of these 400 seconds, 320 seconds is the CPU time and the rest is I/O time. What percentage of elapsed time is spent on I/O operations?

Solution:
Elapsed time = CPU time + I/O time.
This gives us the I/O time = 400 – 320 = 80 seconds at the beginning, which is 20 % of the elapsed time.





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