Modern processors and SoCs require the adoption of power-oriented design styles, due to the implications that power consumption may have on reliability, cost and manufacturability of integrated circuits featuring nanometric technologies. And the power problem is further exacerbated by the increasing demand of devices for mobile, battery-operated systems, for which reduced power dissipation is mandatory. A large fraction of the power consumed by a synchronous circuit is due to the clock distribution network. This is for two reasons: First, the clock nets are long and heavily loaded. Second, they are subject to a high switching activity.The problem of automatically synthesizing a power efficient clock tree has been addressed recently in a few research contributions. In this paper, we introduce a methodology in which low-power clock trees are obtained through aggressive exploitation of the clock-gating technology. Distinguishing features of the methodology are: (i) The capability of calculating powerful clock-gating conditions that go beyond the simple topological search of the RTL source code. (ii) The capability of determining the clock tree logical structure starting from an RTL description. (iii) The capability of including in the cost function that drives the generation of the clock tree structure both functional (i.e., clock activation conditions) and physical (i.e., floorplanning) information. (iv) The capability of generating a clock tree structure that can be synthesized and routed using standard, commercially-available back-end tools.We illustrate the methodology for power-aware RTL clock tree planning, we provide details on the fundamental algorithms that support it and information on how such a methodology can be integrated into an industrial design flow. The results achieved on several benchmarks, as well as on a real design case demonstrate the feasibility and the potential of the proposed approach.
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