Microprocessor giant Intel is developing a secret plan to extend its 32-bit Pentium 4 product line into the 64-bit realm just in case its designed-from-scratch, pure 64-bit Itanium line falters in the market. A small team of Intel engineers is developing the Pentium 4 extensions (code-named Yamhill) in response to rival AMD, which is introducing a 64-bit chip family called Hammer that works with a 64-bit address space but is compatible with the Pentium line. Intel's Itanium is an all-new design that can emulate the Pentium but not at full speed.

A next-generation Pentium 4 design (code-named Prescott) will feature the Yamhill technologies in silicon when the chip ships in 2003 or 2004. But Intel can turn the Yamhill features on or off, so the company plans to enable them only if customers demand a 64-bit Pentium-style chip. Intel still thinks that an all-new design is the way to go: The Itanium will be more efficient than the Pentium 4, although at the expense of compatibility.

The Yamhill technology is a public-relations problem for Intel because the company has publicly bet its future on the Itanium. Intel engineers working on Yamhill are reportedly forbidden to discuss the project with other Intel employees and in email must refer to the project through special codes and abbreviations. And Yamhill's very existence proves that Intel is worried about AMD, a much smaller rival.