System-level design of power efficient FSMD architectures

Date

2009-05-06T17:37:28Z

Authors

Agarwal, Nainesh

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Abstract

Power dissipation in CMOS circuits is of growing concern as the computational requirements of portable, battery operated devices increases. The ability to easily develop application specific circuits, rather than program general-purpose architectures can provide tremendous power savings. To this end, we present a design platform for rapidly developing power efficient hardware architectures starting at a system level. This high level VLSI design platform, called CoDeL, allows hardware description at the algorithm level, and thus dramatically reduces design time and power dissipation. We compare the CoDeL platform to a modern DSP and find that the CoDeL platform produces designs with somewhat slower run times but dramatically lower power dissipation. The CoDeL compiler produces an FSMD (Finite State Machine with Datapath) implementation of the circuit. This regular structure can be exploited to further reduce power through various techniques. To reduce dynamic power dissipation in the resulting architecture, the CoDeL compiler automatically inserts clock gating for registers. Power analysis shows that CoDeL's automated, high-level clock gating provides considerably more power savings than existing automated clock gating tools. To reduce static power, we use the CoDeL platform to analyze the potential and performance impact of power gating individual registers. We propose a static gating method, with very low area overhead, which uses the information available to the CoDeL compiler to predict, at compile time, when the registers can be powered off and powered on. Static branch prediction is used to more intelligently traverse the finite state machine description of the circuit to discover gating opportunities. Using simulation and estimation, we find that CoDeL with backward branch prediction gives the best overall combination of gating potential and performance. Compared to a dynamic time-based technique, this method gives dramatically more power savings, without any additional performance loss. Finally, we propose techniques to efficiently partition a FSMD using Integer Linear Programming and a simulated annealing approach. The FSMD is split into two or more simpler communicating processors. These separate processors can then be clock gated or power gated to achieve considerable power savings since only one processor is active at any given time. Implementation and estimation shows that significant power savings can be expected, when the original machine is partitioned into two or more submachines.

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Keywords

System-Level, VLSI, Power, CAD, FSMD, Hardware, High-level synthesis, clock gating, power gating, partitioning, CoDeL, Simulated Annealing, ILP, ESL

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