IA-32 Plus 64 Equals What?

After two years of speculation, the truth finally emerged last week—Intel has been working on 64-bit extensions for its x86 processors, and they'll appear in new Xeon server processors by June. The extensions create what Intel calls the IA-32e operating mode, a name that somewhat understates the significance of the change—but IA-64 was already taken. There's already a perfectly good name for the new instruction set, but Intel will never use it: AMD64.

The surprising truth is that Intel is already within a few months of releasing x86 processors that are software compatible with AMD's Opteron and Athlon 64. Intel representatives have assured me that all the software Microsoft is now developing will run on both AMD and Intel platforms.

The 64-bit extensions are present in Prescott, the recently introduced 90nm Pentium 4, although they will not be enabled until the next stepping of this die is available. Nocona, the next dual-processor Xeon based on this new stepping, also has 64-bit support. Nocona has some features not found in Opteron, such as Hyper-Threading and the SSE3 extensions. These features, plus the undeniable might of Intel's marketing department, will put immediate pressure on AMD, probably forcing Opteron price cuts.

Intel may be playing catch-up with the AMD64 instruction set, but it has far better OEM relationships and platform designs that will need little work to take full advantage of 64-bit computing. I think it reasonable to assume that by the end of this year, Intel's 64-bit x86 processors will be outselling AMD's.

It's an even safer bet that Xeon will outsell Itanium in 2004. This observation begs the 64-bit question: Can Intel afford to let Itanium compete with Xeon?

Today, Itanium has many features that Xeon lacks: more bus bandwidth, better floating-point support, and comprehensive internal error detection and correction circuitry. The last feature gives Itanium a tremendous advantage in reliability, availability, and serviceability (RAS), considered critical for enterprise server systems.

As long as Xeon continues to be developed as a derivative of Intel's desktop processors, these server-specific features will not be added to it. AMD, lacking an equivalent of Itanium to protect, will have a greater incentive to differentiate its Opteron and Athlon 64 product lines. If AMD adds RAS features to Opteron, Intel's Xeon group will have no choice but to respond, and Intel's management will not object. Intel will not sacrifice its high-volume server processors to protect a low-volume line.

This scenario will take years to play itself out; in the meantime, Intel will maintain or even increase its pace of investment in Itanium. Just as Intel has waited until the last possible minute before admitting it has adopted AMD64, the company's public commitment to Itanium will not waver until the day it decides to abandon the dual-architecture strategy.

That day may never come. Itanium is the fastest, most scalable server-processor family now on the market, the result of billions of development dollars. Xeon can't possibly be ready to take over Itanium's role in the server market before 2007. By that time, Intel will probably have sold over a million Itanium processors, making Itanium a solid commercial success in the market for high-end servers.

The ultimate fate of Itanium depends on a long series of decisions by Intel and other companies, including AMD, HP, IBM, and Sun. If Intel can keep Itanium sufficiently ahead of Opteron to prevent server OEMs and buyers from being tempted to view Opteron as an Itanium alternative, there will be no need to allow Xeon to encroach on Itanium's turf, assuring Itanium's long-term survival.