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Here's the 1st half of the Executive Summary, for those on a time budget!
EXECUTIVE SUMMARY
In March 2004, approximately one year in advance of the official release of Microsoft® Windows Server™ 2003 x64 Edition, Microsoft.com decided to evaluate the benefits of implementing servers built on the x64-based hardware platform by running prerelease versions of that operating system on production www.microsoft.com Web servers. By April 2005, 100 percent of the production Web servers for Microsoft.com were running on the x64-based hardware and operating system platforms.
The virtual memory address space limitation that is inherent with the 32-bit versions of Microsoft Windows® had increasingly led to challenges in application stability and troubleshooting for the Microsoft.com operations team. With 64-bit versions of Windows, the virtual memory address space for an application is greatly increased. That crucial feature combined with the ability to easily execute 32-bit applications with high performance has resolved what had become the number one issue for the Microsoft.com site—memory contention. The x64-based hardware platform can natively execute 32-bit code at roughly the same performance levels as similarly configured 32-bit hardware, and yet the 32-bit environment within the x64 version of Windows also enables 32-bit applications to run without any code modification, making the platform migration virtually seamless.
The resulting platform upgrade to the x64 version of Windows has drastically increased the mean time between application and Web service recycling for Microsoft.com Web servers, thereby increasing the overall site availability. More impressively, the CPU load on the servers decreased by 50 percent, and page response times for some applications are up to fifteen times faster.