&gt; Given that most of Firefox is in JS so the actual code that you end up running is the JIT output, I&#x27;d be very skeptical it&#x27;s any faster.<p>Most of Firefox is JS? Almost all of the lines of code are C++, as far as I&#x27;m aware. Certainly the UI is drawn using XUL&#x2F;XBL&#x2F;web-stuff, but how often is web performance bounded by <i>UI</i> performance? It&#x27;s bounded by the performance of the rendering engine, and that <i>is</i> C++.<p>&gt; (And if it were, I&#x27;d assume Mozilla would just Intel C for the official builds, too?)<p>Seems unlikely, given the output of ICC is crippled for non-Intel x86 chips (which de-facto means AMD nowadays).