title: Microsoft recommends 32bit IIS 7 AppPools on 64bit machines. Why?
body: <p>Looking at number of resources I've found out this weird recommendation. Or to quote Steve Schofield:</p>
  
  <p>For optimal performance, use x64 based systems running 32 bit mode applicatoin pools. You'll get 4 GB per application pool.</p>
  
  <p><a href="http://forums.iis.net/t/1149410.aspx" rel="nofollow">http://forums.iis.net/t/1149410.aspx</a></p>
  
  <p>Also, same recommendation can be found in this Mix 08 talk - <a href="http://channel9.msdn.com/Events/MIX/MIX08/T06" rel="nofollow">Everything You Need to Know about Diagnostics and Debugging on Microsoft Internet Information Services 7</a></p>
  
  <p>So, what is the reason behind it?</p>
  
  <p>EDIT: Microsoft doesn't recommend this for compatibility, but also for <b>performance</b> reasons and I'm interested in this topic exactly because of that. Here is one more link that better explains what I'm talking about:
  <a href="http://learn.iis.net/page.aspx/201/32-bit-mode-worker-processes/" rel="nofollow">http://learn.iis.net/page.aspx/201/32-bit-mode-worker-processes/</a></p>