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Inventing Itanium: How HP Labs Helped Create the Next-Generation Chip Architecture

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June 2001

When HP rolls out its first computer systems based on the Itanium processor architecture later this month, it'll launch a whole new chapter in high-end computing. But for some HP scientists, the product launch -- a workstation and two servers -- marks the culmination of research that began more than a decade ago.

The Intel Itanium processor is the first generation of the latest processor architecture co-invented by Hewlett-Packard and Intel and produced by Intel. These processors are intended for dynamic Internet-based interactions, complex computations, rich media processing and object- oriented environments.

The Itanium architecture has its roots in research that began in the 1980s, when HP Labs set out to define an architecture that would converge HP's current lines of computer system products. This resulted in what became known as the PA-RISC architecture (Reduced Instruction Set Computing).

Recognizing that RISC-based architecture would reach its limits, HP Labs began a research program in Instruction Level Parallelism (ILP) in early 1989, with the goal of evolving the Very Long Instruction Word (VLIW) style of architecture to be more applicable to general-purpose workloads. This research program, which continued through 1996, yielded the EPIC style of architecture and the compiler technology for it.

At about the same time the ILP work began, HP Labs started a separate program to build an EPIC architecture to replace PA-RISC. What emerged by 1993 was the PA-WideWord architecture -- the basis of the HP-Intel alliance and the Itanium processor specification (formerly known as IA-64).

Itanium was developed as an extremely parallel high-performance architecture, carrying out more instructions in one clock than its architectural predecessors. It does this by passing the burden of instruction scheduling to the compiler software that reorders the code for maximum parallelism while the hardware focuses on executing the instructions issued to it.

Read about some of the scientists who contributed to this effort, the technical reports behind the research or go to the HP Itanium Web site.


Bill Worley - one of the principal architects of
PA-RISC and PA-Wide Word
Profile (2001)

Rajiv Gupta - headed the joint architecture team

Jerry Huck - lead architect, Itanium processor specification
Profile (2001)

Bob Rau - VLIW pioneer who helped create the EPIC style of architecture (Deceased, 2002)

Mike Schlansker - lead research on EPIC, a principal architect of PA-Wide Word (bio)

Vinod Kathail - lead research on EPIC, architect of EPIC compiler prototype

Dick Lampman, now Senior Vice President, Research, Hewlett-Packard and Director, HP Labs, managed the PA-Wide Word project. (bio)

Technical Reports

ILP Overviews
Instruction-Level Parallel Processing (1992)
Instruction-Level Parallel Processing: History, Overview and Perspective (1992)

The Hewlett-Packard PA-RISC 8500 Processor (1998)

EPIC Architecture Research
EPIC: An Architecture for Instruction-Level Parallelism Processors (1999)
Achieving High Levels of Instruction-Level Parallism with Reduced Hardware Complexity (1996)
HPL-PD Architecture Specification: Version 1.1 (1993)
HPL Play-Doh Architecture Specification Version 1.0 (1993)

EPIC Compiler Research

Listing below represents only most recent reports - for earlier reports on this subject, see www.hpl.hp.com/techreports/index.html.)

Efficient Backtracking Instruction Schedulers (2000)
Control CPR: A Branch Height Reduction Organization for EPIC Architectures (1999)
Elcor's Machine Description System: Version 3.0 (1998)
Machine-Description Driven Compilers for EPIC Processors (1998)
Meld scheduling: A Technique for Relaxing Scheduling Complaints (1997)
Analysis of Predicted Code (1996)
Profile-Driven Instruction Level Parallel Scheduling (1996)


» Some of the Scientists Who Helped Invent Itanium
» Some of the Research Leading to Itanium (technical reports)
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