Performance improvement of vlsi circuits with clock scheduling

Kapucu, Kerem
Clock scheduling is studied to improve the performance of synchronous sequential circuits. The performance improvement covers the optimization of the clock frequency and the peak power consumption, separately. For clock period minimization, cycle stealing method is utilized, in which the redundant cycle time of fast combinational logic is transferred to slower logic by proper clock skew adjustment of registers. The clock scheduling system determines the minimum clock period that a synchronous sequential circuit can operate without hazards. The timing of each register is adjusted for operation with the minimum clock period. The dependence of the propagation delays of combinational gates on load capacitance values are modeled in order to increase the accuracy of the clock period minimization algorithm. Simulation results show up to 45% speed-up for circuits that are scheduled by the system. For peak power minimization, the dependence of the switching currents of circuit elements on the load capacitance values are modeled. A new method, namely the Shaped Pulse Approximation Method (SPA), is proposed for the estimation of switching power dissipation of circuit elements for arbitrary capacitive loads. The switching current waves can accurately be estimated by using the SPA method with less than 10% normalized rms error. The clock scheduling algorithm of Takahashi for the reduction of the peak power consumption of synchronous sequential circuits is implemented using the SPA method. Up to 73% decrease in peak power dissipation is observed in simulation results when proper clock scheduling scheme is applied to test circuits.


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Citation Formats
K. Kapucu, “Performance improvement of vlsi circuits with clock scheduling,” M.S. - Master of Science, Middle East Technical University, 2009.