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64-bit Computing is on Track to Become a Practical Reality

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AMD and Intel 64-bit desktop and workstation processors can finally run a beta 64-bit version of Windows.
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64-bit Computing is on Track to Become a Practical Reality

AMD and Intel 64-bit desktop and workstation processors can finally run a beta 64-bit version of Windows.


Although many high-end PC users have adopted processors supporting AMD64 and EM64T (also called x64) instructions, the promise of 64-bit desktop computing is still quite a ways off for most users. Although 64-bit versions of Linux have been available for some time, most desktop PC users with 64-bit processors have been looking for a 64-bit version of Windows.

While there is an officially released 64-bit version of Windows XP on the market now, it is only for the Itanium IA-64 (Intel Architecture 64-bit) processors, and not x64. For now, those waiting for an x64 version must set their sights on Windows Server 2003 x64, which is currently available in beta form and due for release to manufacturing sometime in the first half of 2005.

The wait is likely to be longer for those looking for a desktop version of Windows XP that supports the x64 architecture. While Windows XP Professional x64 is available in beta form now, it will most likely take until at least 2006 for this product to be released to manufacturing, which is about how long it will take for the necessary drivers to be ready as well.

This article mainly discusses the beta version of Windows XP Professional x64 Edition, currently available to the public in a free trial version which can be used for 360 days after installation.

Supported Processors

Microsoft Windows XP Professional x64 Edition supports both AMD and Intel desktop/workstation 64-bit processors, specifically:

  • AMD Athlon 64

  • AMD Opteron

  • Intel Xeon with EM64T support

  • Intel Pentium 4 with EM64T support

It's worth noting here that Intel EM64T is virtually identical to the Athlon 64/Opteron's AMD64 extensions, enabling the same 64-bit operating systems and applications to run on processors from both companies.

That said, the x64 edition is not compatible with the Intel Itanium family of processors and for obvious reasons, it is not compatible with 32-bit processors, either. If you attempt to install it on a system running a 32-bit processor (Pentium 4, Athlon XP, and so on) or an Itanium, you will get this error message: "This version of Windows cannot be installed on this machine."

Other Hardware Requirements

Your system also needs to meet or exceed the following specifications:

  • 512MB of RAM*

  • 4GB* available hard disk space

  • Super VGA (800x600 video)

  • CD-ROM/DVD-ROM drive

  • Keyboard

  • Microsoft Mouse or compatible

Virtually any 64-bit system easily exceeds these minimums.

*These minimums are higher than those listed on the Microsoft website, but are provided by the Setup readme file (XP_AMD64.TXT) on the installation CD.

Breaking 32-bit Memory Barriers

The biggest reasons to try Windows XP Professional x64 Edition are its support for more physical (RAM) memory and for more virtual (disk) memory

32-bit versions of Windows and 32-bit processors such as the AMD Athlon XP, Intel Pentium 4 and Intel Xeon (non-EM64T compatible) are limited to 4GB of physical memory. Larger amounts of data must be handled by virtual (disk) memory. Windows XP Professional 64-bit Edition can use up to 16GB of RAM, enabling you to break the 4GB barrier and process huge amounts of data in RAM for greater speed.

Similarly, virtual memory has been increased from 64GB maximum to 16TB (terabytes – a terabyte is 1 trillion bytes)!

Getting Windows XP Professional x64 Edition

You can order a CD (free – pay only shipping and handling) or download a CD image from the Microsoft website at http://www.microsoft.com/windowsxp/64bit/evaluation/upgrade.mspx

Registering for the software download requires the completion of a short form. You must provide your email address so that a link to the downloadable CD image and the product key you will need to install the CD can be sent to you.

Initially, the CD and download are available only in English. Check the Microsoft website for additional language versions.

The installation CD download is in ISO (CD image) format. To create a CD from this file, follow the instructions provided with your CD-mastering software to create a CD from an ISO image. This is not the same process you normally follow to create a data CD. You will need one (1) blank disc to create the installation CD.

It's important to note here that Windows XP's built-in CD-burning software wizard cannot be used to create a CD from an ISO image: you must use a third-party program such as Roxio Easy Media Creator, Nero Burning ROM, or something similar.

The download is about 490MB. If you have a dial-up modem or an ISDN connection, you should order the CD instead.

Installation Options

You can install Windows XP Professional x64 Edition as a clean install or in a dual-boot configuration. It cannot be installed as an upgrade over an existing installation of 32-bit Windows XP.

Because Windows XP Professional x64 Edition is a beta, it should not be used for production. In fact, I'd recommend installing it on a separate system for testing and experimentation instead of on your normal work (or play) PC.

If you must use the same PC for x64 Edition as for your normal work, check your BIOS Setup to see if you can select the boot drive at startup. Some recent systems offer this option. If your system offers this option, you can install a separate ATA/IDE or SATA hard disk, select this disk at startup, and install x64 Edition on that drive. When you turn on your computer, you can select which drive to use for booting your computer.

Windows on Windows 64

The major difference between the installation CD for the 64-bit version of Windows XP Professional and normal 32-bit versions is the AMD64 folder. This folder contains 64-bit drivers and operating system code as well as WOW 64, Microsoft's Windows on Windows technology for running 32-bit applications on a 64-bit operating system. WOW 64 acts as a translation layer between 32-bit applications and Windows, but with minimal impact on performance.

What Works, What Doesn't

Essentially, Windows XP Professional x64 Edition is a 64-bit version of Windows XP Professional SP2, containing enhancements such as enhanced Wi-Fi support, the improved firewall, and Bluetooth support. Virtually all 32-bit Windows applications will work. However, the following won't work with x64:

  • Software which uses Microsoft .NET Framework 1.1

  • Software which uses 16-bit installers

  • Software for Windows 3.1 and MS-DOS

  • 32-bit Device Drivers

32-bit software which uses later versions of .NET Framework must use a 64-bit version; 32-bit versions of .NET Framework cannot be installed on a 64-bit version of Windows.

Driver Issues

Perhaps the biggest problem with running Windows XP Professional x64 is driver support. Devices connected to a Windows x64-based system must use 64-bit drivers. Many 64-bit drivers are supplied on the installation CD; however these cover only common or popular devices. You may not find drivers for the latest hardware, although with new hardware you may find that the manufacturer provides 64-bit drivers you can download. If drivers aren't available they may be under development and slated for a future release. Older hardware on the other hand may prove to be especially problematic because it is unlikely for companies to develop new 64-bit drivers for hardware that is no longer being manufactured.

During Setup, you will be notified of any drivers or software which are not compatible with Windows XP Professional x64 Edition. If you try to install a device using a 32-bit driver, you will be greeted with messages such as "Cannot Install this Hardware", and "Driver is not intended for this platform." Basically if you can't find a 64-bit driver for a device, you won't be able to use it.

Before Windows XP Professional x64 Edition is shipped (most likely sometime in 2006), I anticipate that an x64 Edition-specific catalog will be available on the Microsoft website. If you have hardware which is not supported by drivers on the x64 Edition CD, contact your hardware vendor for updated drivers.


The only significant difference between Windows XP Pro and Windows XP Pro x64 Edition is support for greater than 4GB of memory. Consider that most users aren't even close to exceeding the 4GB memory limitations in Windows XP, in which case moving to Windows XP x64 won't do much for them. And even if Windows XP x64 does support more than 4GB, there aren't many desktop PC motherboards that allow more than 4GB of memory to be installed anyway. What this really means is that for most people, the only reason to install the beta of Windows XP Pro x64 Edition today would be for pure testing and experimentation purposes. With a 360-day beta test period, there's plenty of time to determine whether your existing hardware and software is compatible, and if any of your applications will benefit from the large memory capacity support which 64-bit computing opens up.

For Further Research

Learn more about and order the new x64 Edition public beta by visiting the official Microsoft website at http://www.microsoft.com/windowsxp/64bit/default.mspx

Paul Thurrott's SuperSite for Windows provides an excellent history of the development of the x64 Edition and his experiences with various builds at http://www.winsupersite.com/showcase/windowsxp_x64_preview.asp

GamePC provides a helpful diagram of how WOW 64 works as part of its coverage of the initial private release of what was then referred to as the AMD64 Edition of Windows XP http://www.gamepc.com/labs/print_content.asp?id=amd64xp

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