Feb 10, 2011 17:07 GMT  ·  By

During the evolution from Beta to Release Candidate Microsoft introduced in excess of 2,000 changes designed to improve browser performance.

In a phone conversation we’ve had yesterday, Rob Mauceri, Group Program Manager of IE, and Ryan Gavin, Senior Director of IE underlined that the work done to boost performance in Internet Explorer 9 was focused on real world customer scenarios, and not on besting rivals in any specific benchmark.

Assuring me that the performance team for IE9 never sleeps, Rob and Ryan emphasized that Internet Explorer 9 Release Candidate comes with improvements spanning over 11 browser subsystems.

Internet Explorer 9 RC starts faster, loads webpages faster, and allows you to interact with web pages faster than ever before,” the software giant revealed.

At the same time, the work poured into improving overall performance for IE9 gets a tangible feel when measured with tools such as the WebKit SunSpider Benchmark.

According to Microsoft, thanks to its JS engine Chakra, IE9 RC is now the fastest browser in the JavaScript SunSpider Benchmark.

When it comes to JS, IE9 RC delivers 35% more performance than IE9 Beta which was released on September 15th, 2010, and is no less than 20 times faster than Internet Explorer 8, which is nothing short of impressive.

Chakra has been fine-tuned for the common patterns that users can find across real-world websites.

“Examples of this include significant performance optimizations to JavaScript Closures and object oriented programming patterns, more efficient code generation patterns, and improved JavaScript type system lookups - all patterns commonly found in web applications such as Facebook and Gmail. Chakra uses advanced techniques traditionally only found in desktop optimizing compilers,” the company explained.

The focus with IE9 has always been on driving an increase in performance overall, rather than focusing on the JS subsystem, or any subsystem for that matter.

The number of JavaScript Callbacks-Per-Second has been increased in Internet Explorer 9 RC to as much as 250. This is quite a jump, considering that IE6, IE7, IE8 and IE9 Beta only managed as much as 64 callbacks-per-second.

“Many websites and JavaScript frameworks use programming patterns that yield to the browser in the middle of a computation and then receive a callback after a specified duration, like highly interactive web applications such as games. For some programming patterns, the more callbacks the JavaScript receives, the faster the website responds,” the software giant stated.

The default cache size for temporary Internet files was 50MB in previous IE releases, another detail which changes with the release of IE9 RC. Users will now be able to take advantage of more network cache and enhanced cache heuristics.

“Based on significant customer data, Internet Explorer 9 RC has increased the size of the temporary Internet files to 250MB, which means that Internet Explorer 9 RC can store more resources locally on the PC. In addition, based on significant customer telemetry, Internet Explorer 9 RC has improved the algorithms that decide which resources should be retained in the cache to maximize page load times,” Microsoft said.

IE9 RC Supports HTML5 Geolocation, Advances Interoperability

IE9 Privacy and Security Evolve with the RC, Tracking Protection Now Available

IE9 RC Sports a UI Facelift

Internet Explorer 9 (IE9) Release Candidate (RC) Build 9.0.8080.16413 is available for download here.