The Heart of the

By Jim Turley  |  Posted 2002-02-11 Print this article Print

Beast: A Modified VLIW Core"> Internally, Itanium is a six-issue processor, meaning it can profitably handle six instructions simultaneously. Its also a VLIW (very long instruction word) machine with some enhancements for added flexibility in instruction groupings, less code expansion than classic VLIW designs, and better scalability, to permit wider parallel instruction issue in future IA-64 processors. Thus Intel prefers the term EPIC: Explicitly Parallel Instruction-set Computing. Itanium has nine execution units and future IA-64 processors will probably have more. The nine are grouped into two integer units, two combo integer-and-load/store units, two floating-point units, and three branch units. These four groups are significant, as we shall see in a moment.
Heres a simplified Itanium block diagram:
Itanium block diagram And heres a more complex block diagram: Intel Block Diagram Itanium has a 10-stage pipeline, which is respectable but not impressive by todays standards. Again, future IA-64 processors may have different and probably longer pipes. For comparison, Pentium III has a 12-stage pipeline, but the Alpha 21264 has just eight stages. And Pentium 4 has 20 stages (from the point of fetching micro-ops from its trace cache), and Athlon has 10 stages. Heres a basic Itanium pipeline diagram: 10 Stage In-Order Core Pipeline

Jim Turley is a semiconductor industry analyst, editor, and presenter working in Silicon Valley. Focus technologies are 32-bit microprocessors and semiconductor intellectual property (SIP).

Most recently Jim was the Senior Vice President of Strategy & Technology at ARC International plc (LSE:ARK), where he set the Company's strategic direction and guided its technical developments at five locations worldwide. With headquarters in London (UK) and development centers in New Hampshire, Canada, and California, ARC International is an innovative leader in the semiconductor IP (intellectual property) industry.

Previously, Jim was senior analyst for MicroDesign Resources (a unit of Cahners/Reed Elsevier) as well as the Senior Editor of the prestigious industry journal Microprocessor Report (a three-time winner of the Computer Press Award), and Editor-in-Chief of Embedded Processor Watch. He also hosted and directed the yearly Embedded Processor Forum conference, the industry's annual showcase for new microprocessors. As an analyst and editor, Turley consulting with leading semiconductor firms, providing informed advice on technology trends and market requirements, and was often called on to participate in new product reviews, strategy sessions, and technology development for large semiconductor companies.

Turley is the author of six popular books including Advanced 80386 Programming Techniques, the best-selling PCs Made Easy and others published by McGraw-Hill and Academic Press. He's served as technical editor for several of McGraw-Hill's computer and programming books. In addition, he was a regular technology columnist for Embedded System Programming, Computer Design, and Supermicro magazines, and contributed articles to dozens more. Earlier in his career, Turley held engineering or marketing positions at Adept Technology, Force Computers, TeleVideo, and other high-technology firms in Europe and the United States.

Turley has created and presented numerous seminars and training sessions around the world covering technology trends and the competitive microprocessor market. He is also a well-known speaker at industry events such as the Embedded Systems Conference and Microprocessor Forum, is frequently quoted in the Wall Street Journal, New York Times, USA Today, San Francisco Chronicle, and San Jose Mercury News, and has appeared frequently on television, radio, and Internet broadcasts. Jim volunteers for Recording for the Blind and recently earned his amateur auto-racing license. He has a talented and stunningly attractive wife, two overachieving children, an apparently brain-damaged dog, and an opossum living under the house.

Jim can be contacted at or by calling (408) 226-8086.

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