Real Time Systems

Past Exams

The questions he asked maybe tricky, but the answer most of the time is simple.
Prof. will draw a table for you. First row is properties, first column is the name of task.
What should I know before I schedule a real-time systems?
Hint: Number of CPU, preemptable, period, deadline, WCET, Utilisation
What is utilisation? Explain to me.
He will give you the period, WCET and Deadline of each task
Calculate the utilisation of each task
After you calculate the utilisation, he will ask you these tasks are schedulable or not?
Hint: Single processor cannot, but multiple processors can.
If you have 2 processor how can you schedule these tasks?
Hint: Dispatch these tasks into different processor
He will spilt the tasks for you, and tell him how to schedule.
Hint: Use EDF or RM
He will question you more details, and make sure you fully understand EDF and RM
Hint: In RM, there is Harmonic Task, the schedule utilisation is 1
Then he will ask you which 2 chapters you don't want to be asked.
Most of time he will jump to hardware, then the question is about Cache Colouring (basic idea of it).
Hint: [Youtube: Virtual Memory: 6 Address Translation ] explained the basic of cache and virtual address, it can help you to understand the cache colouring.
Last topic for me is CAN bus. Explain the CAN bus bitwise arbitration
Tricky question: if one node always send message, what will happen to the bus?