A system is designed as a cascade of of 4 subsystems, each contributing the same amount of time to the average service time of the system. If we wish to increase the speed of the system by a factor of 2 by reducing the service time of each subsystem equally, how much speedup should be applied to each subsystem?
This is how I solved the problem and I was hoping someone could let me know if I am on the right track:
Amdahl's Law is Speed Up[overall] = 1 / (Fe/Se + (1 - Fe)) where Fe is enhanced fraction and Se is enhanced speedup. In this case Speed Up overall = 2 and enhanced speed up = 4 because there are 4 subsystems. All I did was solve for Fe and I got .66, which is 66.66%. This means each subsystem must increase it's speed by 66.66%.
Is this correct? Am I on the right track at all?
The next question asks a similar question except the average times of the first two subsystems are to be reduced by twice as much as those of the last two subsystems, but the overall speed up should remain at 2. I'm a little confused how to use Amdahl's Law here.
Would appreciate all / any advice or any literature that might help.