The No. 1 deliverable of 64-bit is a significant boost in the amount of memory a system can use. At the high end of the Windows line, Windows Server 2003 Data Center x64 Edition supports up to 1TB of RAM, compared with 64GB of RAM for the Data Center version in 32-bit. Likewise, Windows XP Professional x64 Edition supports 128GB of physical RAM, compared with 4GB of RAM in the 32-bit version. The x64 editions of both Windows Server 2003 and Windows XP Professional are available now. More RAM means fuller processor use and potentially better performance because systems running Windows x64 can feed more data to the processor per clock cycle and reduce swapping to disk by loading and retaining more work in RAM.You might also bump into trouble mixing 64-bit code with 32-bit IE plug-insnearly all of themand with add-ons for the Windows Explorer graphical shell. Windows x64 ships with 32-bit and 64-bit versions of IE but only 64-bit Windows Explorer. In addition, Windows x64 wont run 16-bit code, which tends to lurk in easily overlooked portions of applications such as installer tools. These 16-bit programs must be rewritten to run on Windows x64. In a few of these cases, such as with some InstallShield Software Corp. and Acme installers, Microsoft has coded Windows x64 to recognize the incompatible 16-bit installers and transparently substitute included 32-bit versions during the applications install process. Another potential trouble point is Windows Server 2003 Service Pack 1: Both versions of Windows x64 are based on the Windows Server 2003 SP1 code base, so sites experiencing application compatibility issues with the new service pack will need to get them straightened out before deploying Windows x64. The Windows x64 editions arent Microsofts first 64-bit operating system forays; the company has been shipping versions of Windows XP and Windows Server 2003 for Intels Itanium platform for the past few years. However, the Windows x64 editions ship with a fairly long list of services and applications that Microsoft left out of its Itanium port. Windows components making their 64-bit debut in these releases include Windows Firewall and Security Center, support for DVD video playback, Windows Messenger, Remote Assistance, Power Management, System Restore and Bluetooth. Next page: Migration has its rough spots.
One of the most dramatic cases for upgrading to Windows x64 is that of Windows Terminal Server: With 32-bit Windows, the number of Terminal Services users that a machine can support is capped by the platforms 2GB kernel space limit. In Windows x64, this limit has been expanded to 8TB of kernel space and 8TB of user space, which means sites with RAM-stacked servers can take better advantage of those resources today and have a good deal of headroom for future expansion.