A distinctive feature of the engine is that it JIT compiles scripts on a separate CPU core, parallel to the web browser.
[4] SunSpider tests performed on November 18, 2009 showed the PDC version of IE9 executing scripts much faster than IE8, but slower than Firefox 3.6, Chrome 4, and WebKit Nightly.
[3] The same test performed on March 15, 2010 showed the first IE9 Platform Preview (using the then-current version of Chakra) to be faster than Firefox (with SpiderMonkey), but slower than Safari (with SquirrelFish Extreme), Chrome (with V8), and Opera (with Carakan).
On March 8, 2011, Microsoft published results showing the 32-bit Internet Explorer 9 to be faster than Safari, Firefox (with TraceMonkey), Chrome, and Opera.
[5] March 2011 performance tests for ZDNET concluded that Internet Explorer 9 (32-bit), Chrome 10, and Firefox 4 release candidate were "pretty evenly matched.