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Unformatted text preview: nto practical Ever-increasing clock frequencies mean that maintaining global synchrony is getting harder; clock skew (the difference in the clock timing at different points on the chip) compromises performance and can ultimately lead to circuit malfunction. High clock rates also lead to excessive power consumption. The clock distribu tion network can be responsible for a significant fraction of the total chip power consumption. Although clock-gating techniques can give a degree of control over the activity of the clock net, this is usually coarse-grained and can adversely affect clock skew. Global synchrony maximizes supply current transients, causing electromagnetic interference. EMC (Electromagnetic compatibility) legislation is becoming more stringent, and increasing clock rates make compliance ever more challenging. Motivation for self-timed design For these reasons, asynchronous design techniques have recently attracted renewed interest as they address the above problems as follows: There is no problem with clock skew because there is no clock. An asynchronous design only causes transitions in the circuit in response to a request to carry out useful work, avoiding the continuous drain caused by the clock signal and the overhead of complex power management systems. It can switch instantaneously between zero power dissipation and maximum performance. Since many embedded applications have rapidly varying workloads, an asynchronous processor appears to offer the potential of significant power savings. Asynchronous circuits emit less electromagnetic radiation owing to their less coherent internal activity. 376 The AMULET Asynchronous ARM Processors In addition, an asynchronous circuit has the potential to deliver typical rather than worst-case performance since its timing adjusts to actual conditions whereas a clocked circuit must be toleranced for worst-case conditions. The AMULET series of asynchronous microprocessors was developed at the University of Manchester, in England, as one aspect of the growing global research into asynchronous design. There are other examples of asynchro...
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This document was uploaded on 10/30/2011 for the course CSE 378 380 at SUNY Buffalo.
- Spring '09