The 64-bit Intel Xeon -- formerly code-named Nancona -- is a hybrid 32/64 bit CPU, which can run both 32- and 64-bit software via a set of 64-bit instruction-set extensions. The 64-bit version of Prescott, which had only been hinted at previously, was expected to be a desktop chip. Now, Intel says it's positioned as a server part for OEMs.

The confusing product positioning is becoming a hallmark of the so-called hybrid arena. AMD kicked off the category a little more than a year ago when it debuted its AMD64 architecture and companion extensions. These are implemented in AMD's Opteron server and Athlon desktop processors. Intel's extensions, which it first used in the Xeon and are called EM64T, are compatible with AMD's extensions.

Until this announcement by IBM, it hadn't been clear whether Intel would move out its 64-bit extensions beyond Xeon to its Pentium processors.

In May, at its spring analysts meeting for the business community, Intel president Paul Otellini said that Intel was building the capability for its 64-bit extensions into Prescott. At the time, he said that Intel wouldn't enable the feature until Microsoft released a 64-bit version of Windows; that operating system is expected later this year.

Now, in the wake of the release of the IBM blade servers, an Intel spokesman says it is not releasing the 64-bit enabled Prescott as a retail processor. Instead, it is offered as an OEM part intended for use in servers, not desktops.

As for IBM's non-Prescott boxes released, they include six eServer xSeries systems based on the Intel 3.6-GHz 64-bit Xeon.

Separately, Dell is releasing four new PowerEdge servers equipped with the Xeon. The rollouts mark the first Tier 1 servers for the new 3.6-GHz Xeon.

IBM is painting the new servers as its biggest product rollout for the line since it was launched four years ago.

"These servers will replace all of the current two-way systems and, eventually, the uniprocessor line, in our xServer," says Stuart McRae, IBM's xServer marketing manager. "These systems will allow much richer configurations for our business partners. They will be able to go in and innovate and provide some differentiation for customers."

Xeon-equipped servers from HP are also expected to be announced shortly.