title: When will the virtual page number have more bits than the physical frame number?
body: <p>I have the following question on a practice exam:</p>
  <blockquote>
  <p>For a computer system that implements paging, under what circumstance will the VPN (virtual page number) have more bits than the PFN (physical frame number)?</p>
  </blockquote>
  <p>I am trying to argue that:</p>
  <blockquote>
  <p>The number of bits to represent the virtual page number and physical frame number equal are equal. Even if the system doesn't have enough memory available to fill the entire physical address space, the same number of bits will be used.</p>
  <p>On the 80386 processor, 20 bits are used for the virtual page number and there are 20 bits are used to represent physical frame numbers.</p>
  </blockquote>
  <p>Is there a circumstance where the VPN will have more bits than the PFN?</p>