6 bits wide repeat the estimates for both 32 and 16

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Unformatted text preview: re to work in this style. Support for self-timed design from the tools industry is also lacking. The AMULET processor cores are research prototypes, developed at the University of Manchester in England, and their commercial future is not yet clear. There is insufficient space in this book to present complete descriptions of them, but they are outlined here since they represent another, very different way to implement the ARM instruction set. See the 'Bibliography' on page 410 for references where further details on AMULET1 and AMULET2e may be found. Fuller details on AMULETS will be published in due course. The latest self-timed core, AMULET3, incorporates most of the features found in the clocked ARM cores, including support for the Thumb instruction set, debug hardware, an on-chip macrocell bus which supports system-on-chip modular design, and so on. It brings the asynchronous technology up to the point where it is ready to enter commercial use, and the next few years will tell if this technology has a role to play in the future of the ARM architecture. 374 Self-timed design 375 14.1 Self-timed design Today, and for the past quarter of a century, virtually all digital design has been based around the use of a global 'clock' signal which controls the operation of all of the components of the system. Complex systems may use multiple clocks, but then each clocked domain is designed as a synchronous subsystem, and the interfaces between the different domains have to be designed very carefully to ensure reliable operation. Clocks have not always been so dominant. Many of the earliest computers employed control circuits which used local information to control local activity. However, such 'asynchronous' design styles fell out of favour when highly productive design methodologies based around the use of a central clock were developed to match the demands of an industry with access to integrated circuit technologies which offered rapidly increasing transistor resources. Clock problems problems: Recently, however, clocked design styles have begun to run i...
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This document was uploaded on 10/30/2011 for the course CSE 378 380 at SUNY Buffalo.

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