Birla Institute of Technology (BIT Mesra) 2007 REAL TIME SYSTEMS ( BITS ZG553 ) - Question Paper

Birla Institute of Technology & Science, Pilani

Distance Learning Programmes Division

Second Semester 2006-2007

Mid-Semester Test (EC-1 Regular)



Course No. : BITS ZG553

Course Title : REAL TIME SYSTEMS

No. of Pages = 1

No. of ques. = four
Nature of examination : Closed Book

Weightage : 40%

Duration : two Hours

Date of examination : 03/02/2007 (FN)

Note:

1. Please follow all the Instructions to Candidates provided on the cover page of the ans book.

2. All parts of a ques. should be answered consecutively. every ans should begin from a fresh page.

3. Mobile phones and computers of any type should not be brought inside the exam hall.

4. Use of any unfair means will outcome in severe disciplinary action.



Q.1. ans the subsequent ques. briefly and precisely.

(a) What do you understand by the term “real-time”? How the concept of real-time is various from the traditional notion of time? discuss with suitable example.

(b) What do you mean by an optimal scheduling algorithm?

(c) discuss the various kinds of priority inversions that a task might suffer due to a lower priority task when the Priority Ceiling Protocol is used to share critical resources among a set of tasks.

(d) What do you mean by bandwidth preserving algorithms? When they are used?

(4 + two + two + two = 10)



Q.2. A cyclic scheduler is used to schedule a set of 3 periodic tasks

T1 = (100, 20); T2 = (80, 20) and T3 = (150, 30).



(a) Is the task set schedulable? Justify your ans.

(b) obtain hyperperiod and possible frame size(s) Satisfying all the needed constraints.

(c) Choosing largest frame size, draw a Network Flow Graph for 1 hyperperiod.

(2 + four + six = 12)



Q.3. A system of tasks {T1, T2, T3} = {(5, 1) ;( 8, 3) ;( 13, 4)} is to be scheduled by RMA,

(a) Is the task set schedulable? discuss briefly.

(b) Now if you change task T3 by a new lower priority task (lower than T3) T4, whose execution time is 5, what should be its minimum rate, so that the system is schedulable? (3 + five = 8)



Q.4. Consider the subsequent task set, where release time of the tasks r, their execution time e and priority P is provided. Their requirement of resources is also provided. Draw a schedule diagram for the 5 tasks from time 0 to 20 using the NPCS Protocol. For every task the corresponding critical part begins 1 time unit after the task started executing. every nested critical part begins 1.5 time units after the start of the previous critical part. Lower the number, higher the priority

Earning:   Approval pending.