Invision Power Board 3 Slow Page Rendering

We have an Invision Power Board (IPB) 3 forum hosted on ours erver which is running on a Windows Server 2008 R2 x64 + IIS 7.5 + FastCGI + PHP 5.3 + MySQL stack.

Since an upgrade from IPB 2, the home page (i.e. /forums/) renders in < 0.10 sec but unfortunately all the other forum pages have page render times of > 4 sec (usually around 4.6 sec).

  • I have tweaked every IPB setting I can think of
  • I have tried various tweaks for fastcgi
  • I don’t see any significant CPU usage on the database
  • I have disabled dns lookups for mysql
  • I have enabled PHP wincache and even tried enabling memcached to not much effect.
    … and much much more.

Does anyone have any ideas where we could look next?