328 Registers and Counting

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

The Itanium processor has a massive register set, with 128 general-purpose integer registers (each 64 bits wide), 128 floating-point registers (each 82 bits wide), 64 1-bit predicate registers, 8 branch registers, and a whole bunch of other registers scattered among several different functions, including some for x86 backward compatibility. Like a lot of RISC processors, the first register (GR0) is hard-wired to a permanent zero, making it worthless for storage but useful as a constant for inputs and a bit bucket for outputs. Heres a simplified diagram of key application registers:
IA-64 register set
Heres a detailed diagram of application and system-level register sets: Application Register Set And of course Itanium supports standard 32-bit x86 execution modes and the 32-bit registers are mapped onto the IA-64 registers. See details in the section titled "Dont Look Back: How Itanium Handles x86 Code" down below. What a far cry from the cramped, crowded register set of the x86! With 256 registers to play with, programmers have an embarrassment of riches. To avoid that embarrassment, IA-64 has two features that manage the register file: register frames and register rotating. These require some explanation…

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 info@jimturley.com or by calling (408) 226-8086.

For additional information, visit http://www.jimturley.com.


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