IA-64

In 2008, Itanium was the fourth-most deployed microprocessor architecture for enterprise-class systems, behind x86-64, Power ISA, and SPARC.

During this time, HP had begun to believe that it was no longer cost-effective for individual enterprise systems companies such as itself to develop proprietary microprocessors.

Intel had also been researching several architectural options for going beyond the x86 ISA to address high-end enterprise server and high-performance computing (HPC) requirements.

Intel's goal was to leverage the expertise HP had developed in their early VLIW work along with their own to develop a volume product line targeted at the aforementioned high-end systems that could be sold to all original equipment manufacturers (OEMs), while HP wished to be able to purchase off-the-shelf processors built using Intel's volume manufacturing and contemporary process technology that were better than their PA-RISC processors.

Intel took the lead on the design and commercialization process, while HP contributed to the ISA definition, the Merced/Itanium microarchitecture, and Itanium 2.

[2] Intel's product marketing and industry engagement efforts were substantial and achieved design wins with the majority of enterprise server OEMs, including those based on RISC processors at the time.

Industry analysts predicted that IA-64 would dominate in servers, workstations, and high-end desktops, and eventually supplant both RISC and CISC architectures for all general-purpose applications.

[4][5] Compaq and Silicon Graphics decided to abandon further development of the Alpha and MIPS architectures respectively in favor of migrating to IA-64.

[6] By 1997, it was apparent that the IA-64 architecture and the compiler were much more difficult to implement than originally thought, and the delivery of Itanium began slipping.

[7] Since Itanium was the first ever EPIC processor, the development effort encountered more unanticipated problems than the team was accustomed to.

In 1999, Intel led the formation of an open-source industry consortium to port Linux to IA-64 they named "Trillium" (and later renamed "Trillian" due to a trademark issue), which was led by Intel and included Caldera Systems, CERN, Cygnus Solutions, Hewlett-Packard, IBM, Red Hat, SGI, SuSE, TurboLinux and VA Linux Systems.

As a result, a working IA-64 Linux was delivered ahead of schedule and was the first OS to run on the new Itanium processors.

[19][20][21] Intel has extensively documented the Itanium instruction set[22] and the technical press has provided overviews.

Speculation, prediction, predication, and renaming are under control of the compiler: each instruction word includes extra bits for this.

In practice, the processor may often be underutilized, with not all slots filled with useful instructions due to e.g. data dependencies or limitations in the available bundle templates.

In 2006, with the release of Montecito, Intel made a number of enhancements to the basic processor architecture including:[29]