• Chart: 64-Bit Processors and Products

Intel has announced that some of its future 64-bit processors will implement the x86-64 instruction set, which extends the x86 address and data paths to 64 bits, but still runs 32-bit applications natively. Intel will continue to support the IA-64 architecture used by its Itanium processors, and Microsoft will supply versions of Windows and other software products for both architectures. Although Microsoft’s 64-bit products are coming to market very slowly, Intel’s support for the x86-64 architecture and new security features in these processors should accelerate the use of 64-bit computers for both servers and desktops.

The Key Processor Differences

The key difference between the two 64-bit architectures lies in how they support existing 32-bit applications.

Because Intel’s IA-64 is a new architecture with a new instruction set, it is not natively compatible with the 32-bit applications in use today. Instead, Itanium includes an on-chip translator that converts 32-bit x86 instructions to native IA-64 instructions, a process that results in slower 32-bit performance. Because of this architecture, Intel has promoted 64-bit computing primarily for servers and high-end workstations running new 64-bit applications.

AMD's AMD64/x86-64 architecture, used in Athlon 64 and Opteron processors, extends the original x86 design and instruction set with 64-bit capabilities. All 32-bit programs run natively in this design, and applications that incorporate the new instructions will run as 64-bit applications. AMD promotes 64-bit computing for a wider range of applications, including gaming, mobile computing, desktops, high-end workstations, and servers.

Because of the superior 32-bit performance of the x86-64 design, Intel said at its Feb. 2004 developer conference that it would offer chips with its own version of x86-64 support (IA32e), while continuing to support IA-64.

Microsoft’s 64-Bit Support

Microsoft has previously announced that it will support both 64-bit architectures. Versions of Windows XP, Windows Server 2003, and SQL Server 2000 are already shipping for the IA-64 architecture. Microsoft has released preview (beta) editions of Windows XP and Windows Server 2003 for the AMD64 processors, but SQL Server will not be supported on this platform until the next version, SQL Server 2005 (code-name Yukon), which has been delayed until at least 2005. (For a complete view of the processors, their features, and supporting Microsoft products, see the chart "64-Bit Processors and Products".)

Microsoft has not made clear its intentions regarding 64-bit versions of other products, such as Exchange and BizTalk.

Microsoft has been slower than the open-source community to support both 64-bit processor architectures. Linux distributions such as RedHat and Novell SuSE already provide support for the Linux kernel on both architectures, as does the open-source database MySQL.

Choosing 64-Bit for Security

Although most users will consider upgrading to computers with 64-bit processors to gain improvements in performance or to take advantage of systems with more than 4GB of memory, the 64-bit processor’s execution protection feature could provide worthwhile security benefits.

Execution protection, also called no-execute (NX) support, allows the OS to differentiate between memory locations that contain executable code and those that contain data. Marking memory in this way reduces the likelihood of a buffer overflow, a common software flaw that can be exploited to run malicious code.

Resources

For background on the different 64-bit architectures, see "Support for AMD ‘Hammer’ Hedges 64-Bit Bet" on page 9 of the June 2002 Update.

Microsoft’s 64-bit support for Windows XP is detailed at www.microsoft.com/windowsxp/64bit.

Microsoft’s 64-bit support for Windows Server 2003 is detailed at www.microsoft.com/windowsserver2003/64bit.

Microsoft’s 64-bit support for SQL Server is detailed at www.microsoft.com/sql/64bit.

AMD’s 64-bit processors are described at www.amd.com/us-en/Processors/ProductInformation.

Intel’s 64 bit processors are described at www.intel.com/products.