On April 9, 2003, Microsoft officially announced that it would support AMD's then-upcoming 64-bit Opteron and Athlon 64 microprocessors with 64-bit native versions of Windows XP and Windows Server 2003. The news must have sent shivers down the spines of executives at Microsoft partner Intel, whose 64-bit Itanium product line has languished because of slow performance and incompatibilities with today's existing 32-bit software. For AMD, of course, it was--and still is--a major victory. Not only was the one time microprocessor also-suddenly getting equal press from Microsoft as Intel, within a year, Intel shocked the world by announcing that it would essentially ape AMD's designs and create 64-bit versions of the Xeon and Pentium 4 CPUs that would be code compatible. The follower had suddenly become the leader.

The beauty of AMD's 64-bit processor design, of course, is that it offers the best of both worlds. Based as they are on the 32-bit x86 architecture, the processors are completely compatible with all of the software and operating systems people run today. And unlike the Itanium, it can run those systems at full speed (or better than full speed, if recent benchmarks are to be believed). But the AMD64 platform, as it's come to be known, also offers all of the benefits of 64-bit computing: Primarily, a much wider address space that make it possible to build PCs, workstations, and servers that offer oodles of RAM. Today's 32-bit processors are (essentially) constrained to supporting just 4 GB of RAM, a figure that seemed massive 10 years ago. However, 64-bit versions of Windows will support a 16 terabyte (16 TB) address space. Today's 64-bit systems, of course, are limited by their physical designs, and offer less actual memory support. But 32 GB 64-bit systems are becoming common today, perfect for database servers, 3D graphics work, and other high-end uses.

Few people would doubt that the future of computing is 64-bits. But the slow uptake of the Itanium, in both the server and workstation markets, left market leader Intel with precious little to offer customers (see my 64-bit Windows preview for more information about Microsoft's Itanium-based efforts). However, the two previously mentioned events marked an unprecedented tilt in the history of the PC industry: AMD released an x86-compatible 64-bit line of microprocessors, and Microsoft elected to support it with its best-selling workstation and server operating systems. The 64-bit computing future, it seemed, would be coming sooner than expected.

Microsoft's initial language regarding the AMD64 port was guarded. "The 64-bit versions of Windows XP and Windows Server 2003 for the upcoming AMD Athlon 64 and AMD Opteron processors are designed for use on servers and high-end desktops and workstations [only]," the initial press release reads. "They are expected to increase the efficiency of many operations, including engineering and scientific projects, financial services, online transaction processing, data warehousing, digital content creation, video editing, advanced gaming, and computer-aided design." Hardly sounds exciting, now does it? Consumer acceptance of the new chips--especially among technology enthusiasts and gamers--would soon change Microsoft's outlook, however.

Windows XP 64-Bit Edition for 64-Bit Extended Systems appears

In September 2003, Microsoft shipped its first beta release of what it was now (awkwardly) calling Windows XP 64-Bit Edition for 64-Bit Extended Systems. This 64-bit native operating system was based on the Windows Server 2003 code base and offered compatibility with AMD64 chips like the Opteron and Athlon 64. And Microsoft, naturally, was still touting its high-end possibilities, but with a subtle shift in emphasis to "consumers and business customers [who will want access to] the next generation of high-performance desktop computing, including gaming, digital content creation and video editing."

Microsoft's September 2003 was notable for another reason. For the first time, the company was touting the ability of Windows XP 64-Bit to run 32-bit Windows applications natively and at full speed through its new WOW 64 (Windows on Windows 64) technologies (a WOW 16 in Windows NT let that system run 16-bit DOS and Windows applications). "We've heard from our customers that, until now, the inability to efficiently run 32-bit applications on 64-bit systems has been a major barrier to investing in 64-bit technologies," said Chris Jones, corporate vice president for the Windows Client Division at Microsoft. "With the combination of Windows XP and the new AMD64 processors, customers can be assured of having all the computing power and memory they need, now and into the future, while still being able to run their current applications."

Microsoft made the beta version of Windows XP 64-Bit Edition for 64-Bit Extended Systems available to testers an MSDN subscribers, but the company was still positioning the release as offering a subset of the total feature-set of Windows XP, and this first beta (build 1069) lacked many XP features, including the Luna-style UI themes. However, from a functional standpoint, the beta release was surprisingly stable and full-featured. Without a lot of probing, there was little to suggest that this wasn't the existing 32-bit version of XP. The final release was expected in the first half of 2004, and within months, Microsoft had shipped 20,000 beta copies to customers.

Build 1069 screenshots


A change of priorities

As 2003 moved into 2004, Microsoft's slow road to security with Windows XP Service Pack 2 (SP2) was beginning to change the way the company viewed many of its upcoming products. Longhorn was delayed again, and Microsoft finally decided to make its 64-bit version of XP a true stable mate of its 32-bit brethren. Now, the 64-bit version of XP would feature most of the functionality from the 32-bit version of XP SP2. That development would take more time, but it would result in a more secure product that would better serve customers. Microsoft began talking up a late 2004 release date.

Drivers were another issue. Though the AMD64 platform was designed for full compatibility with 32-bit x86 software, hardware drivers were another issue. Through its partner outreach programs and tradeshows like WinHEC and the PDC, Microsoft had been evangelizing the need for hardware markers to supply 64-bit versions of their drivers. But it was clear that those drivers wouldn't be ready by mid-2004. Internally, Microsoft set a goal to include a default driver set in the box with the 64-bit version of XP that would exceed what the company ships today with XP Home and Professional Editions.

The company was also moving its 64-bit OS closer to the mainstream. Though it was still pushing engineering, CAD/CAM, and digital content creation as potential reasons to adopt an AMD64-based chip, the company was also touting mainstream uses like 3D gaming and video editing. The delays in XP SP2--which necessitated delays in XP 64-bit--meant that the systems it supported would be more readily available whenever it did ship. XP 64-bit was eking its way out of niche status. But the next bit of news would thrust this product firmly into the limelight.

The x64 platform is born

In June 2004, Intel announced that it would market new versions of its Xeon and Pentium 4 microprocessors that would support something called EM64T (Extended Memory 64 Technology), copying AMD's 64-bit processor design. Intel's decision to remain compatible with AMD and not create a completely different design is a boon to customers, but I suspect it had more to do with appeasing Microsoft: It's unlikely the software giant would have dedicated the resources to supporting yet another similar but different 64-bit platform. And besides, Microsoft engineers--especially NT architect David Cutler--had championed the AMD design. Intel was on board.

With Intel's support, the AMD64 design was renamed to the more generic x64 in honor of the x86 name. And by July, Microsoft was revving new updates to its 64-bit Windows Server 2003 and Windows XP products that would support both AMD64 and Intel EM64T-based processors. "Intel's decision marks a mainstream shift to x64," Dennis Oldroyd, the Director of the Windows Server Business Group at Microsoft told me in July.

In August 2004, Microsoft announced simpler new naming for its x64 products, and the XP version was renamed to Windows XP Professional x64 Edition. The company also announced a new beta version, which was far closer to Windows XP SP2 on x86 that previous betas. "We're positioning it as extension of XP Professional family," Brian Marr, the Product Manager of the Windows Client Group at Microsoft told me in mid-August. "Everything in Professional you should expect to find in [XP Pro] x64. Only a few minor items are lost due to the change in technologies and architecture." One example is the 16-bit subsystem: XP Pro x64 won't run any legacy DOS or Win16 applications. Legacy protocols like AppleTalk and NetBEUI are also not supported. "this is an opportunity to clean house on some of those items," Marr confided.

Microsoft had also made concessions in order to reach mainstream consumers with this release. So the new beta release--build 1218--would include such things as Windows Movie Maker, Windows Media Player, the Luna user interface, and most of the other features we've come to expect from XP. The beta also supports the wireless devices, Windows Firewall, and Bluetooth support Microsoft added to XP SP2.

Finally, Microsoft also announced a Technology Exchange Program that will let purchasers of x64-based PCs exchange their 32-bit Windows OS for the x64 version when that becomes available. However, the x64 versions of XP (and Windows Server 2003) don't support upgrading from 32-bit versions: You have to perform a clean install.

"We see XP Pro x64 as being a great operating system," Marr told me. "It's reliable because it's built on the Windows Server 2003 code base, but it also has many of the security features from Windows XP SP2. We've built a fantastic OS for our customers." In keeping with its new feature set, Microsoft delayed the release yet again. Now, Windows XP Pro x64 Edition is due to ship alongside Windows Server 2003 in the first half of 2005.

Build 1218 screenshots


Paul goes 64-bits

In late September 2004, I finally jumped on the 64-bit bandwagon with a Hewlett-Packard Presario a640n desktop machine that I'll use to evaluate various 64-bit products. Currently, the machine is multiple-booting between five operating systems:

- Windows XP Home Edition SP2
- Windows XP Professional x64 Edition build 1218
- Windows XP 64-Bit Edition for 64-Bit Extended Systems build 1069
- Windows Server 2003 Standard x64 Edition with SP1 build 1218
- Windows Server 2003 Enterprise Edition for 64-Bit Extended Systems build 1069

I've only installed the older versions of the products for comparative purposes and have so far spent the most time with XP Pro x64 build 1218. I'll post a full preview of this build soon, but my initial reaction is very positive: The product features virtually every feature I've come to expect from XP, and is compatible with the vast majority of software I install. Only a few XP PowerToys, Windows Media Player 10, and a single game (DOOM 3) have refused to run. All of the machine's hardware is 100 percent compatible, and I've seen no driver issues. Performance is what I'd expect from the machine.

Will I be switching to x64 full time? Sure, but not quite yet. I need to test the system with a wider array of devices and add-ons before I make the move. So though I can't recommend the beta release as a production environment just yet, Windows XP x64 is far more mature than I had expected. It's a very positive sign that Microsoft might just be on the right track.