How Epic is EPIC

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

?"> Is EPIC really VLIW? Yes, by most definitions of that term. Pedantic computer architects may argue over abstruse differences, and Intels marketing people will steam over the misuse of their trademark, but for all intents and purposes, EPIC is merely a more pronounceable rendition of VLIW with a few enhancements. Few, if any, of EPICs features discussed so far are unique to Itanium or to Intel. Broadsiding a processor with a volley of instructions at once is what VLIW is all about. EPIC corrupts, if you will, the pure ideal of VLIW by introducing its peculiar 5-bit instruction templates that unnecessarily complicates multi-instruction issue and effectively eliminates several potential combinations of instructions. On the plus side, Intel gets credit for allowing flexible-sized instruction groupings, which help increase issue efficiency. This is likely to payoff handsomely in future IA-64 processors. IA-64s groups also reduce the code bloat seen in traditional VLIW designs (where fixed-width VLIW instruction slots may often go unused if the compiler cannot find independent instructions to group together from within a particular window of instructions).
Certainly there are plenty of processors with multiple execution units and microarchitectures that can keep them busy. Predicated execution is nothing new, either. Tiny embedded processors do it, and compiler writers are happy to manage the multiple predicate bits. Itaniums scoreboard bits, register frames, and svelte and RISC-like instruction set all have been seen before. Itanium doesnt even reorder instructions, for cryin out loud, something even midrange 32-bitters do all day long. But then again, Intels formally stated goal was to shift complexity out of the processor logic and to the compiler. Yet, if you read a presentation from last Intel Developer Forum, youll see that "Future Itanium Processor Family processors can have out-of-order execution." Of course, this also implies that McKinley will be called Itanium II or something similar.
IA-64 doesnt really introduce anything all that new. Its more of an amalgam of concepts and techniques seen before and given the ol Intel twist. That doesnt make it bad, but its also not spectacular nerd porn.

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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