title: VHDL: Conditionally Instantiate Components using Generics
body: <p>I'd like to conditionally instantiate components using generics set on the command line.  I'd prefer to have a string as the generic (i.e. <code>fast</code> or <code>slow</code>) rather than a number.</p>
  
  <p>I can't find any examples of this on stackOverflow so I thought I'd ask.</p>