Demonstration of Speed and Power Enhancements on an Industrial Circuit Through Application of Clock Skew Scheduling

Abstract

A strategy to enhance the speed and power characteristics of an industrial circuit is demonstrated in this paper. It is shown that nonzero clock skew scheduling can improve circuit performance while relaxing the strict timing constraints of the critical data paths within a high speed system. A software tool implementing a nonzero clock skew scheduling algorithm is described together with a methodology that generates the required clock signal delays. Furthermore, a technique that significantly reduces the power dissipated in the noncritical data paths is demonstrated. The application of this technique combined with nonzero clock skew scheduling to the slower data paths is also described. Speed improvements of up to 18% and power savings greater than 80% are achieved in certain functional blocks of an industrial high performance microprocessor.

Clock distribution networks in synchronous digital integrated circuits

“…The primary attributes of the multiplier; repetitive circuit elements, abutted or closely spaced layouts, extremely high throughput (i.e., many hundreds of megahertz) due to heavy pipelining, make the multiplier an important class of VLSI system that requires highly specialized clock distribution networks. [212], [213] The fundamental design trend in current microprocessors has been the development of systems operating at high clock frequencies; specifically, greater than 1-GHz operating frequencies. The primary difficulty in satisfying the goal of achieving these high clock rates is the delay uncertainty caused by process and environmental variations such as on-chip process parameter and temperature variations and related design-oriented issues such as voltage gradients, capacitive and inductive coupling, and load impedance mismatches.…”

“…The application of clock skew scheduling has also been demonstrated on a similar microprocessor architecture in [213]. Both speed and power are enhanced through the use of clock skew scheduling.…”