Shortly after AMD announced its plans for an x86-based 64-bit chip, I wrote an editorial ("Clash of the 64-Bit Architectures," Winter 2000, http://www.winnetmag.com, InstantDoc ID 15895) in which I said that Intel's lock on the 64-bit—processor market and the cost of supporting multiple 64-bit hardware platforms made Microsoft's adoption of the 64-bit AMD architecture look "about as likely as seeing pigs fly." But as one reader with an especially keen memory for editorial prognostication recently pointed out to me, Microsoft's announcement that it would offer native support for the 64-bit AMD Opteron processor in both Windows Server 2003 and Windows XP proved that pigs do occasionally take to the air.

Two Radically Different Animals
With the current adoption levels of 64-bit computing on PCs almost nil, Microsoft's announcement might not seem earthshaking, but it's an important step for both Microsoft and businesses. In the 32-bit market, processor offerings from Intel and AMD are binary-compatible. However, the companies' 64-bit products aren't compatible. Intel's 64-bit Itanium processor and AMD's 64-bit Opteron processor are as different as night and day.

Intel designed the Itanium for the high-end server market. The Itanium's new Explicitly Parallel Instruction Computing (EPIC) architecture is essentially incompatible with the x86 architecture used in 32-bit Pentium, Celeron, AMD Athlon, and AMD Duron processors. To enable the Itanium to run 32-bit x86 executable programs, Intel added an x86 emulation layer to the processor, and a substantial performance penalty accompanies that layer. To take advantage of the EPIC architecture and ensure that 32-bit applications run well on the Itanium, you must use a 64-bit Itanium-compatible compiler to recompile those applications.

Taking the opposite approach, the Opteron is essentially an evolutionary step in the x86 architecture. Because it still uses the x86 instruction set, the Opteron is completely binary-compatible with today's 32-bit x86 programs. To run native 64-bit programs, the Opteron uses AMD's extended 64-bit x86 instruction set.

Who's in the Lead?
At first glance, the AMD approach might appear to be the hands-down winner because it can run both 64-bit applications and earlier 32-bit applications with no performance penalty. However, this approach does have a trade-off. Although the Opteron offers better 32-bit compatibility than the Itanium does, the Opteron quite possibly—even probably—won't be able to reach the same ultimate level of performance as Intel's newer EPIC architecture.

No one is more aware of the limitations of the x86 architecture than Intel, and it wouldn't abandon that architecture without careful consideration. In taking the long-term, no-compromise approach, Intel gambled that the EPIC architecture would be able to offer better performance and be more likely to eventually achieve performance levels that the earlier x86 architecture would never be able to reach.

Although most desktop users probably won't enjoy the benefits of 64-bit computing in the near future, the faster processors are already beginning to gain a foothold in the database server market. Microsoft SQL Server 2000 Enterprise Edition (64-bit) running on Itanium-based hardware captured first place in the nonclustered Transaction Processing Performance Council (TPC) performance standings earlier this year. The 64-bit chip's performance will appeal to enterprises that need the fastest available speeds. Even if your business's demands aren't that lofty, you can safely assume that today's future technology will become tomorrow's standard technology.

And the Winner Is ...
Although the question of which architecture and company will win the battle for the 64-bit marketplace remains unresolved, Microsoft's support for both platforms results in a win-win-win situation. Microsoft wins because Windows' ability to span multiple hardware platforms will appeal widely to enterprise customers. AMD certainly wins because without native 64-bit Windows support, the Opteron's potential market would be just a fraction of what it could be otherwise. Even Intel wins, because AMD's 64-bit offering will help drive the adoption of 64-bit technology and verify the viability of 64-bit computing. And, of course, businesses will benefit as competition in the 64-bit market ensures that prices and performance are competitive.