title: ifort 64 bit build; ifort 64 vs. gfortran 64
body: <p>I have what I imagine will be an easy question.  How do I create a 64-bit build using ifort?  I&#39;m using &quot;ifort -Ofast -o program.exe <em>.f</em>&quot;.  I&#39;ve set the compilervars to intel64 and am working on win7 using a xeon processor.  I&#39;ve looked through the menu of compiler flags but haven&#39;t been able to identify what I need.  I see there&#39;s a -m64 option for mac users but that won&#39;t help me.  </p>
  
  <p>A second question, would there be that big of a performance issue between a gfortran -m64 build relative to the same using ifort?</p>
  
  <p>Thanks!</p>