Clash of the 64-Bit Architectures

Intel and AMD vie for the 64-bit computing market

In a market in which OEMs and independent software vendors (ISVs) quickly adopt new technology advances to gain extra bullet points on their promotional literature, mainstream 64-bit computing is looming on the horizon. But 64-bit computing brings with it some big decisions for vendors and consumers—decisions that are sure to slow acceptance of the new platform. Next-generation 64-bit systems will have to choose between two competing processor standards—Intel's IA-64 architecture and AMD's x86-64 architecture—each of which has its own native 64-bit specifications with vastly different implementations.

More than Just Clock Speed
Intel's abandonment of its flagship x86 architecture in favor of the radically different IA-64 architecture represents a significant move by Intel into the high-end server and workstation markets. Intel's announcement that the first Itanium (formerly code-named Merced) chips would run at a modest 733MHz wasn't what the industry expected, though, considering that Pentium systems already run at speeds in excess of 1GHz. However, in the case of Itanium, the chip offers much more than clock speed.

Itanium will change the way we measure processor performance. Itanium's Explicitly Parallel Instruction Computing (EPIC) architecture lets the chip process up to six instructions per cycle, a design that gives the processor the potential ability to perform more work within a given clock cycle. To get a true sense of Itanium's processing power, we'll need to consider instructions per clock cycle (IPC) in addition to the chip's clock speed.

However, taking advantage of this new architecture requires advances in compiler technology to produce code optimized for the chip. This requirement and the fact that Itanium will run 32-bit applications in emulation mode make it pretty hard to get too excited about the 733MHz Itanium. Given Intel's history, you know that faster systems will be right around the corner. Running existing 32-bit applications through hardware emulation means that all those 32-bit applications that will likely remain the software standard for some time to come will take a significant performance hit. Despite the new architecture, adopting any of the first-generation Itanium systems will be a hard sell.

A Wedge in the 64-Bit Platform
Choosing not to follow Intel's lead, AMD has struck out on its own 64-bit course and extended the existing x86 architecture into the 64-bit world. AMD's upcoming 64-bit processor (code-named Sledgehammer) is virtually the opposite of Itanium: Sledgehammer will run at speeds rivaling the fastest 32-bit processors and will be 100 percent compatible with 32-bit applications. However, Sledgehammer's native 64-bit instruction set is completely unlike Itanium's. Sledgehammer's x86-64 processors require completely different binary images from Itanium's IA-64 processors—not unlike what the i386 and Alpha required for Windows NT.

And the Winner Is ...
Industry support is the key to market adoption, and Intel has that support. Almost all the major Windows ISVs have already lined up behind Intel and the Itanium chip. The list of vendors committed to supporting Itanium reads like the Who's Who of the software industry: Microsoft, IBM, Hewlett-Packard (HP), Dell, Compaq, and NEC are all there. The ball is in Microsoft's court regarding any possible Windows compatibility with Sledgehammer's native 64-bit mode. Unless Microsoft has an unexpected change of heart, the future of Sledgehammer probably lies with Linux or as a fast 32-bit chip running 32-bit versions of Windows.

Right now, we're all benefiting from Intel and AMD's 32-bit rivalry in which the companies are taking turns holding the reigning processor speed title. However, I don't see that situation happening in the 64-bit world; Intel appears to have a lock on the 64-bit CPU technology—at least for the Windows 2000 platform. Supporting different hardware platforms is expensive for software companies—even Microsoft. Not very long ago, Microsoft and Compaq pulled Alpha support out of Win2K, and Alpha was already a well-established 64-bit processor. Seeing Microsoft adopt the AMD chip is about as likely as seeing pigs fly.

That factor doesn't mean that the AMD chip is devoid of supporters. Sledgehammer seems destined to become a UNIX processor. Sun Microsystems has already announced that it will port its Solaris UNIX OS to the x86-64 platform, and a Linux port is under way as well. What a shame (and considering the Department of Justice—DOJ—case, how ironic) that 64-bit Windows users won't get the same benefits of competition that 32-bit Windows users have right now.

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