Amdahl’s Law
SAmdahl(N) = [1 + fs]/[1/N +fs]
where S is the speedup on N processors and fs is the serial (non-parallelizable) fraction of the work to be done.
Amdahl says that in the limit of an infinite number of processors, S cannot exceed [1+ fs ]/ fs. So, for example if fs = 0.01, S cannot be greater than 101 no matter how many processors are used.