title: Can't enable multiple CPU on VirtualBox
body: <p>I would like to use more than one CPU to run <a href="https://en.wikipedia.org/wiki/Ubuntu_version_history#Ubuntu_14.04_LTS_.28Trusty_Tahr.29" rel="noreferrer">Ubuntu&nbsp;14.04</a> (Trusty Tahr) 32-bit in VirtualBox, but when I stop the machine and go in <em>Settings</em> &rarr; <em>System</em> &rarr; <em>Processor</em>, the processor(s) slider is grayed out as you can see in the screenshot image. How can I enable this feature?</p>
  
  <p>Host OS: Windows 10 Pro 64-bit <br/>
  Guest OS: Ubuntu 14.04 32-bit <br/>
  VirtualBox: Version 5.1.22 r115126 <br/>
  Processor: Intel(R) Core(TM) i7-3770 CPU @ 3.40 GHz (8 CPUs), ~3.4 GHz</p>
  
  <p><a href="https://i.stack.imgur.com/4lLBk.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/4lLBk.jpg" alt="Enter image description here"></a></p>
  
  <p>PS: My problem in the first instance is that the Ubuntu virtual machine is extremely slow and I would like to improve the performance, so any suggestion for that would also be welcome.</p>