title: Where is the point at which adding additional cores or CPUs doesn’t improve the performance at all?
body: <blockquote>
    <p>*Adding a second core or CPU might increase the performance of your parallel program, but it is unlikely to double it. Likewise, a
    four-core machine is not going to execute your parallel program four
    times as quickly— in part because of the overhead and coordination
    described in the previous sections. However, the design of the
    computer hardware also limits its ability to scale. You can expect a
    significant improvement in performance, but it won’t be 100 percent
    per additional core, and there will almost certainly be a point at
    which adding additional cores or CPUs doesn’t improve the performance
    at all.</p>
  </blockquote>
  
  <p>*</p>
  
  <p>I read the paragraph above from a book. But I don't get the last sentence.
  So, Where is the point at which adding additional cores or CPUs doesn’t improve the performance at all?</p>