SQL Server 2005 is the first SQL Server release to natively support Itanium and x64-based 64-bit processors. A single SQL Server 2005 source code base is compiled for three platforms: x86 (32-bit), Itanium (64-bit), and x64 (64-bit). SQL Server 2005 (64-bit) can run on Itanium-based servers with Windows Server 2003 Service Pack 1. SQL Server 2005 (64-bit) for the x64 platform can run on Windows XP x64 Professional 2003 (64-bit) or on Windows Server 2003 x64, which is based on the code for Windows Server 2003 SP1. In addition, you can run SQL Server 2005 (32-bit) on x64-based hardware and operating systems, such as Windows XP x64 Professional 2003 and Windows Server 2003 SP1 64-bit x64, in WOW64 mode.
WOW64 mode, also known as extended system support, is a feature of 64-bit editions of Microsoft Windows that allows 32-bit applications to execute unmodified on a 64-bit system. Applications function normally in 32-bit mode even though the underlying operating system is running on the 64-bit platform.
SQL Server 2005 (32-bit) supports up to 32 processors, and SQL Server 2005 (64-bit) supports up to 64 processors.
Here are some of the enhancements in SQL Server 2005 (64-bit) compared to SQL Server 2000 (64-bit):
SQL Server 2000 (64-bit) does not include management and monitoring tools such as Enterprise Manager, Query Analyzer, Profiler, Analysis Manager, and so on. SQL Server 2005 (64-bit) bundles all the management tools, including SQL Server Management Studio, Profiler, Database Engine Tuning Advisor, SQL Server Configuration Manager, and so on.
Only Enterprise Edition of SQL Server 2000 (64-bit) is supported on 64-bit platforms, and SQL Server 2000 Service Pack 4 is required for x64 support. Both Standard and Enterprise Editions of SQL Server 2005 (64-bit) support 64-bit computing, which includes both the Intel Itanium 2 family of processors and the x64 family of processors from both Intel and AMD. In addition, Standard Edition does not have a memory limitation and is only limited to the level of memory supported by the version of Windows on which you run the product.
SQL Server 2000 (64-bit) and SQL Server 2005 (64-bit) do not support MAPI-based SQL Mail. However, on SQL Server 2005 (64-bit) you can use SMTP-based Database Mail to send emails from T-SQL code.
The SQL Server 2005 database engine and other subsystems are better aware of the 64-bit architecture than SQL Server 2000. Therefore, SQL Server 2005 can effectively make use of 64-bit computing to provide better performance and system throughput.
SQL Server 2000 (64-bit) does not allow designing and running Data Transformation Services (DTS) packages. SQL Server 2005 (64-bit), on the other hand, fully supports SQL Server Integration Services (SSIS). You can use Business Intelligence Development Studio on a 64-bit machine to design, debug, and run an SSIS package. Also, because SSIS packages are saved as XML files (with the .dtsx file extension), you can create a package on one platform (for instance, on a 32-bit server) and then edit or run that package on another platform (for instance, on a 64-bit server).
SQL Server 2000 Reporting Services and SQL Server 2000 Notification Services do not support 64-bit systems. SQL Server 2005 Notification Services is supported on both x64 and Itanium platforms. However, Notification Services Management Objects (NMO) is not supported in WOW64 mode on AMD and Intel x64 platforms. SQL Server 2005 Reporting Services is also supported on both x64 and Itanium platforms; however, a few things, such as the RSKeyMgmt.exe tool, subscription deliveries to reports in TIFF format, and so on, are not fully implemented.
Side-by-side installation of 32-bit SQL Server 2000 SP4 on an x64 platform with SQL Server 2005 (64-bit) is not supported.