Amdahl law and parallelism
Your terminology is incorrect.  Amdahl's law is a way of estimating performance of a parallel program.  It is not a "programming model".  Amdahl's law says that if there is a computation, part of which is $M$ sequential (not parallelizable) instructions and part of which is $N$ instructions which could be parallelized, and you have $P$ processors, then the shortest computation time you can hope for is:
$$ M + \frac{N}{P}. $$

So the speedup with $P$ processors is:
$$ \frac{M+N}{M+\frac{N}{P}}. $$

Which, in the limit as $P \gg N$ goes to
$$ \frac{M+N}{M} = 1 + \frac{N}{M}. $$

The takeaway message is simply that you shouldn't fool yourself.  $N/M$ is much more important than $N/P$.